Projection exposure methods and apparatus, and projection optical systems

ABSTRACT

A dioptric projection optical system for imaging a reduced image of a pattern on a first surface onto a second surface using radiation-transmitting refractors. The projection optical system has a front lens unit of a positive refracting power and a rear lens unit of a positive refracting power. An aperture stop is located in the vicinity of a rear focal point of the front lens unit.

This is a Division of application Ser. No. 09/856,959 filed May 29,2001, now abandoned which in turn is a National Stage of PCT/JP00/06706filed Sep. 28, 2000. The entire disclosure of the prior application(s)is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to projection exposure apparatus andmethods used in fabrication of microdevices, for example, such assemiconductor integrated circuits, imaging devices including CCDs andthe like, liquid crystal displays, or thin-film magnetic heads by thelithography technology, and to projection optical systems suitablyapplicable to such projection exposure apparatus. The present inventionalso relates to methods of fabricating the foregoing projection exposureapparatus and projection optical systems.

BACKGROUND ART

As the circuit patterns for such microdevices as the semiconductorintegrated circuits and others are becoming finer and finer in recentyears, the wavelengths of illumination light(radiation) for exposure(exposure light(radiation)) used in the exposure apparatus such assteppers and the like have been decreasing toward shorter wavelengthsyear after year. Namely, as the exposure light, KrF excimer laser light(wavelength: 248 nm) is going mainstream in place of the i-line(wavelength: 365 nm) of mercury lamps mainly used conventionally, andArF excimer laser light of a much shorter wavelength (wavelength: 193nm) is also nearing practical use. For the purpose of further decreasingthe wavelength of the exposure light, there are also attempts to usehalogen molecular lasers and others like the F₂ laser (wavelength: 157nm).

Although the aforementioned excimer lasers, halogen molecular lasers,etc. are available as light sources in the vacuum ultraviolet region ofwavelengths not more than 200 nm, there are limits to practical bandnarrowing thereof.

Since limited materials transmit the emitted light in this vacuumultraviolet region, available materials are limited for lens elementsconstituting the projection optical systems and transmittances of thelimited materials are not so high, either. As matters now stand, theperformance of antireflection coats provided on surfaces of the lenselements is not so high, as against those for longer wavelengths.

A first object of the present invention is to suppress chromaticaberration of the projection optical system and reduce loads on thelight source.

A second object of the present invention is to correct chromaticaberration for the exposure light having some spectral width, by addinga single kind of glass material or a few color-correcting glassmaterials.

A third object of the present invention is to obtain an extremely finemicrodevice circuit pattern while simplifying the structure of theprojection optical system.

A fourth object of the present invention is to obtain an extremely finemicrodevice circuit pattern without decrease in throughput.

DISCLOSURE OF THE INVENTION

For accomplishing the foregoing first or second object, a firstprojection optical system according to the present invention is adioptric projection optical system for forming an image of a pattern ona first surface, onto a second surface by action of light-transmitting(radiation-transmitting) refractors, comprising: a front lens unithaving a positive refracting power, located in an optical path betweenthe first surface and the second surface; a rear lens unit having apositive refracting power, located in an optical path between the frontlens unit and the second surface; and an aperture stop located in thevicinity of a rear focus position of the front lens unit; the projectionoptical system being telecentric on the first surface side and on thesecond surface side, wherein the following condition is satisfied:

0.065<f2/L<0.125,

where f2 is a focal length of the rear lens unit and L is a distancefrom the first surface to the second surface.

A first fabrication method of a projection optical system according tothe present invention is a method of fabricating a dioptric projectionoptical system for forming an image of a pattern on a first surface,onto a second surface by action of radiation-transmitting refractors,comprising: a step of locating a front lens unit having a positiverefracting power; a step of locating a rear lens unit having a positiverefracting power, between the front lens unit and the second surface;and a step of locating an aperture stop between the front lens unit andthe rear lens unit; wherein the front lens unit, the rear lens unit, andthe aperture stop are located so that the projection optical system istelecentric on the first surface side and on the second surface side,and said method using the projection optical system satisfying thefollowing condition;

0.065<f2/L<0.125,

where f2 is a focal length of the rear lens unit and L a distance fromthe first surface to the second surface.

For accomplishing the foregoing first or second object, a secondprojection optical system according to the present invention is adioptric projection optical system for forming an image of a pattern ona first surface, onto a second surface by action ofradiation-transmitting refractors, comprising three or more lenseshaving their respective refracting powers, wherein when three lenses areselected in order from the first surface side of the lenses having theirrespective refracting powers, at least one surface of the three lensesis of an aspheric shape having a negative refracting power.

For accomplishing the foregoing first or second object, a thirdprojection optical system according to the present invention is adioptric projection optical system for forming an image of a pattern ona first surface, onto a second surface by action ofradiation-transmitting refractors, comprising a plurality of lenseshaving their respective refracting powers, wherein when two lenses areselected in order from the first surface of the lenses having theirrespective refracting powers, at least one surface of the two lenses isan aspheric surface, and wherein, where Ca is a local, principalcurvature near a center of an optical axis of the aspheric surface andCb is a local, principal curvature in the meridional direction of anextreme marginal region of a lens clear aperture diameter of theaspheric surface, the following condition holds if the aspheric surfacehas a negative refracting power:

Cb/Ca<0.7  (b-1);

on the other hand, in the present invention, the following conditionholds if the aspheric surface has a positive refracting power:

Cb/Ca>1.6  (b-2).

In this invention, the local, principal curvature Ca near the center ofthe optical axis of the aspheric surface and the local, principalcurvature Cb is in the meridional direction of the extreme marginalregion of the lens clear aperture diameter of the aspheric surface canbe expressed as follows as an example. That is to say, the asphericsurface is expressed by the following equation (b-3): $\begin{matrix}\begin{matrix}{{Z(Y)} = \quad {\frac{Y^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right){Y^{2}/r^{2}}}}} +}} \\{\quad {{{AY}^{4} + {BY}^{6} + {CY}^{8} + {DY}^{10} + {EY}^{12} + {FY}^{14}},}}\end{matrix} & \text{(b-3)}\end{matrix}$

where Y is a height of the aspheric surface from the optical axis, z adistance along the direction of the optical axis from a tangent plane atthe vertex of the aspheric surface to the aspheric surface, r a radiusof curvature at the vertex, κ a conical coefficient, and A, B, C, D, E,and F aspheric coefficients.

With this expression, the local, principal curvatures Ca and Cb aregiven as follows.

Ca=1/r  (b-4)

$\begin{matrix}{{Cb} = \frac{d^{2}{z/d^{2}}Y}{\left\{ {1 + \left( {{dz}/{dY}} \right)^{2}} \right\}^{3/2}}} & \text{(b-5)}\end{matrix}$

With increase in the numerical apertures of the projection opticalsystems and with increase in the size of the image field, there areincreasing demands for minimization of distortion. In order to correctonly distortion while suppressing influence on the other aberrations, itis preferable to place an aspheric surface for correction of distortionat a position as close to the object plane (mask) as possible. On thisoccasion, when the aspheric surface satisfies the foregoing condition(b-1) or (b-2), the distortion can be corrected well even with increasein the numerical aperture and with increase in the size of the imagefield.

For accomplishing the foregoing first or second object, a fourthprojection optical system according to the present invention is adioptric projection optical system for forming an image of a pattern ona first surface, onto a second surface by action ofradiation-transmitting refractors, comprising four or more lenses havingtheir respective refracting powers, wherein when four lenses areselected in order from the first surface of the lenses having theirrespective refracting powers, at least one surface of the four lenses isan aspheric surface, and wherein, where Ca is a local, principalcurvature near a center of an optical axis of the aspheric surface andCb is a local, principal curvature in the meridional direction of anextreme marginal region of a lens clear aperture diameter of theaspheric surface, the following condition holds if the aspheric surfacehas a negative refracting power:

Cb/Ca<0.45  (c-1);

on the other hand, in the present invention, the following conditionholds if the aspheric surface has a positive refracting power:

Cb/Ca>2.3  (c-2).

In the present invention, the local, principal curvatures Ca, Cb can beexpressed by the above equations (b-4) and (b-5) as an example. When theaspheric surface satisfies the foregoing condition (c-1) or (c-2), thedistortion can be corrected well even with increase in the numericalaperture and with increase in the size of the image field.

For accomplishing the foregoing third object, a fifth projection opticalsystem according to the present invention is a projection optical systemfor forming a reduced image of a pattern on a first surface, onto asecond surface, comprising: in the order named hereinafter from thefirst surface side, a first lens unit having a negative refractingpower; a second lens unit having a positive refracting power; a thirdlens unit having a negative refracting power; a fourth lens unit havinga positive refracting power; an aperture stop; and a fifth lens unithaving a positive refracting power; wherein the following conditions aresatisfied:

−1.3<1/β1<0, and

0.08<L1/L<0.17,

where β1 is a composite, lateral magnification of the first lens unitand the second lens unit, L1 is a distance from the first surface to alens surface closest to the second surface in the second lens unit, andL is a distance from the first surface to the second surface.

A second fabrication method of a projection optical system according tothe present invention is a method of fabricating a projection opticalsystem for forming a reduced image of a pattern on a first surface, ontoa second surface, comprising: a step of preparing a first lens unithaving a negative refracting power; a step of preparing a second lensunit having a positive refracting power; a step of preparing a thirdlens unit having a negative refracting power; a step of preparing afourth lens unit having a positive refracting power; a step of preparingan aperture stop; a step of preparing a fifth lens unit having apositive refracting power; and a step of locating the first lens unit,the second lens unit, the third lens unit, the fourth lens unit, theaperture stop, and the fifth lens unit in the order named from the firstsurface side; wherein, where β1 is a composite, lateral magnification ofthe first lens unit and the second lens unit, L1 a distance from thefirst surface to a lens surface closest to the second surface in thesecond lens unit, and L a distance from the first surface to the secondsurface, the first and second lens units are prepared so as to satisfythe following condition:

−1.3<1/β1<0,

and the first and second lens units are located so as to satisfy thefollowing condition:

0.08<L1/L<0.17.

For accomplishing the foregoing third object, a sixth projection opticalsystem according to the present invention is a projection optical systemfor forming a reduced image of a pattern on a first surface, onto asecond surface, comprising at least one light-transmitting refractorlocated in an optical path of the projection optical system, wherein thefollowing condition is satisfied:

0.46<C/L<0.64,

where C is a total thickness along the optical axis of the radiationtransmitting refractor located in the optical path of the projectionoptical system and L is a distance from the first surface to the secondsurface.

A third fabrication method of a projection optical system according tothe present invention is a method of fabricating a projection opticalsystem for forming a reduced image of a pattern on a first surface, ontoa second surface, comprising a step of preparing a first lens unithaving a negative refracting power, a step of preparing a second lensunit having a positive refracting power, a step of preparing a thirdlens unit having a negative refracting power, a step of preparing afourth lens unit having a positive refracting power, a step of preparingan aperture stop, a step of preparing a fifth lens unit having apositive refracting power, and a step of locating the first lens unit,the second lens unit, the third lens unit, the fourth lens unit, theaperture stop, and the fifth lens unit in the order named from the firstsurface side, wherein the first lens unit to the fifth lens unit areprepared so as to satisfy the following condition:

0.46<C/L<0.64,

where C is a total thickness along the optical axis of alight-transmitting refractor located in an optical path of theprojection optical system and L a distance from the first surface to thesecond surface.

For accomplishing the foregoing third object, a seventh projectionoptical system according to the present invention is a projectionoptical system for forming a reduced image of a pattern on a firstsurface, onto a second surface, comprising at least three lens surfacesof aspheric shape, wherein the following condition is satisfied:

0.15<Ea/E<0.7,

where E is the total number of members having their respectiverefracting powers among radiation-transmitting refractors in theprojection optical system and Ea the total number of members eachprovided with a lens surface of aspheric shape.

A fourth fabrication method of a projection optical system according tothe present invention is a method of fabricating a projection opticalsystem for forming a reduced image of a pattern on a first surface, ontoa second surface, comprising: a step of preparing light-transmittingmembers so that at least three surfaces of lens surfaces of theradiation-transmitting refractors are of aspheric shape and so that thefollowing condition is satisfied:

 0.15<Ea/E<0.7,

where E is the total number of members having their respectiverefracting powers among the radiation-transmitting refractors and Ea thetotal number of members each provided with a lens surface of asphericshape; and a step of assembling the radiation transmitting members.

A first projection exposure apparatus according to present invention isa projection exposure apparatus for projecting a reduced image of apattern provided on a projection master, onto a workpiece to effectexposure thereof, comprising: a light source for supplying exposurelight; an illumination optical system for guiding the exposure lightfrom the light source to the pattern on the projection master; and theprojection optical system being either one selected from said projectionsystems; wherein the projection master can be placed on the firstsurface of the projection optical system, and the workpiece be placed onthe second surface.

A second projection exposure apparatus according to the presentinvention is a projection exposure apparatus for projecting a reducedimage of a pattern provided on a projection master, onto a workpiece toeffect exposure thereof while scanning, comprising: a light source forsupplying exposure light; an illumination optical system for guiding theexposure light from the light source to the pattern on the projectionmaster; the projection optical system being either one selected fromsaid projection optical systems; a first stage for enabling theprojection master to be placed on the first surface of the projectionoptical system; and a second stage for enabling the workpiece to beplaced on the second surface; wherein the first and second stages aremovable at a ratio of speeds according to a projection magnification ofthe projection optical system.

For accomplishing the foregoing fourth object, a third projectionexposure apparatus according to the present invention is a projectionexposure apparatus for projecting a reduced image of a pattern providedon a projection master, onto a workpiece to effect exposure thereof,comprising: a light source for supplying exposure light in a wavelengthregion of not more than 180 nm; an illumination optical system forguiding the exposure light from the light source to the pattern on theprojection master; and a projection optical system located in an opticalpath between the projection master and the workpiece, the projectionoptical system guiding 25% or more by quantity of the exposure lighthaving passed through the projection master, to the workpiece to formthe reduced image of the pattern on the workpiece.

A first projection exposure method according to the present invention isa projection exposure method of projecting a pattern formed on aprojection master, onto a workpiece to effect exposure thereof, whichuses the projection exposure apparatus being either one of theprojection exposure apparatus, wherein the projection master is placedon the first surface and the workpiece is placed on the second surface,and wherein an image of the pattern is formed on the workpiece throughthe projection optical system.

A fourth projection exposure apparatus and a second projection exposuremethod according to the present invention are a projection exposureapparatus and a projection exposure method for projecting a reducedimage of a pattern provided on a projection master, onto a workpiece toeffect exposure thereof, which comprise: a light source for supplyingexposure light in a wavelength region of not more than 200 nm; anillumination optical system for guiding the exposure light from thelight source to the pattern on the projection master; and a projectionoptical system located in an optical path between the projection masterand the workpiece, the projection optical system guiding the exposurelight having passed through the projection master, to the workpiece toform the reduced image of the pattern on the workpiece; wherein thefollowing condition is satisfied:

(En4/En3)>(En2/En1)

where En1 is a quantity of the exposure light traveling from the lightsource to the illumination optical system, En2 a quantity of theexposure light traveling from the illumination optical system to theprojection master, En3 a quantity of the exposure light entering theprojection optical system, and En4 a quantity of the exposure lightemerging from the projection optical system toward the workpiece.

A first microdevice fabrication method according to the presentinvention is a method of fabricating a microdevice having apredetermined circuit pattern, comprising: a step of projecting an imageof the pattern onto the workpiece to effect exposure thereof, using theforegoing exposure method; and a step of developing the workpiece afterthe projection exposure.

Next, for accomplishing the foregoing first or second object, a fifthprojection exposure apparatus according to the present invention is aprojection exposure apparatus for projecting a pattern on a projectionmaster onto a workpiece to effect exposure thereof, comprising: anillumination optical system for supplying exposure light of a wavelengthof not more than 200 nm to the projection master; and a projectionoptical system for forming an image of the pattern on the projectionmaster, at a predetermined projection magnification β on the workpiece;wherein the projection optical system comprises an aperture stop, afront lens unit located between the aperture stop and the projectionmaster, and a rear lens unit located between the aperture stop and theworkpiece, wherein, where y (kg) represents a translated amount offluorite of a disk member from an amount of fluorite amonglight-transmitting optical materials in the projection optical system,f2 (mm) represents a focal length of the rear lens unit, and NAwrepresents a maximum numerical aperture on the image side of theprojection optical system, and where a parameter x is defined asfollows:

x=f2·4|β|·NAw ²;

the following conditions are satisfied:

y≦4x−200,

y≦(4x/13)+(1000/13),

y≧4x−440, and

y≧0.

A sixth projection exposure apparatus according to the present inventionis a scanning projection exposure apparatus for projecting a pattern ona projection master onto a workpiece to effect exposure thereof whilescanning, comprising: an illumination optical system for supplyingexposure light of a wavelength of not more than 200 nm to the projectionmaster; and a projection optical system for forming an image of thepattern on the projection master, at a predetermined projectionmagnification β on the workpiece; wherein the projection optical systemcomprises an aperture stop, a front lens unit located between theaperture stop and the projection master, and a rear lens unit locatedbetween the aperture stop and the workpiece, wherein, where y (kg)represents a translated amount of fluorite of a disk member from anamount of fluorite among light-transmitting optical materials in theprojection optical system, f2 (mm) a focal length of the rear lens unit,and NAw a maximum numerical aperture on the image side of the projectionoptical system, and where a parameter x is defined as follows:

x=f2 . 4|β|. NAw ²;

the following conditions are satisfied:

y≦4x−200,

y≦(4x/13)+(1000/13),

y≧4x−440, and

y≧0.

A seventh projection exposure apparatus according to the presentinvention is a projection exposure apparatus for projecting a pattern ona projection master onto a workpiece to effect exposure thereof,comprising: an illumination optical system for supplying exposure lightof a wavelength of not more than 200 nm to the projection master; and aprojection optical system for forming an image of the pattern on theprojection master, at a predetermined projection magnification β on theworkpiece; wherein the projection optical system comprises an aperturestop, a front lens unit located between the aperture stop and theprojection master, and a rear lens unit located between the aperturestop and the workpiece, wherein, where y (kg) represents a translatedamount of fluorite of a disk member from an amount of fluorite amonglight-transmitting optical materials in the projection optical system,f2 (mm) a focal length of the rear lens unit, and NAw a maximumnumerical aperture on the image side of the projection optical system,and where a parameter x is defined as follows:

x=f2 . 4|β|. NAw ²;

the following conditions are satisfied:

y≦(9x/2)−270,

y≦90,

y≧(9x/2)−(855/2), and

y≧0.

An eighth projection exposure apparatus according to the presentinvention is a projection exposure apparatus for projecting a pattern ona projection master onto a workpiece to effect exposure thereof,comprising: an illumination optical system for supplying exposure lightof a wavelength of not more than 200 nm to the projection master; and aprojection optical system for forming an image of the pattern on theprojection master, at a predetermined projection magnification β on theworkpiece; wherein the projection optical system comprises an aperturestop, a front lens unit located between the aperture stop and theprojection master, and a rear lens unit located between the aperturestop and the workpiece, wherein, where y (kg) represents a translatedamount of a first material of a disk member from an amount of the firstmaterial among light-transmitting optical materials in the projectionoptical system, f2 (mm) represents a focal length of the rear lens unit,and NAw represents a maximum numerical aperture on the image side of theprojection optical system, and where a parameter x is defined asfollows:

x=f2 . 4|β|. NAw ²;

the following conditions are satisfied:

y≦4x−200,

y≦(4x/13)+(1000/13),

y≧4x−440, and

y≧0.

Next, for accomplishing the foregoing first or second object, a thirdprojection exposure method according to the present invention is aprojection exposure method of projecting a pattern on a projectionmaster onto a workpiece to effect exposure thereof, comprising: anillumination step of supplying exposure light of a wavelength of notmore than 200 nm to the projection master; and an image forming step offorming an image of the pattern on the projection master, at apredetermined projection magnification β on the workpiece, using aprojection optical system comprising a front lens unit, an aperturestop, and a rear lens unit; wherein the image forming step comprises afirst auxiliary step of guiding the light from the projection master tothe front lens unit, a second auxiliary step of guiding the lightpassing through the front lens unit, to the aperture stop, a thirdauxiliary step of guiding the light passing through the aperture stop,to the rear lens unit, and a fourth auxiliary step of forming the imageof the pattern on the workpiece, using the light passing through therear lens unit, wherein, where y (kg) represents a translated amount offluorite of a disk member from an amount of fluorite amonglight-transmitting optical materials in the projection optical system,f2 (mm) represents a focal length of the rear lens unit, and NAwrepresents a maximum numerical aperture on the image side of theprojection optical system, and where a parameter x is defined asfollows:

x=f2 . 4|β|. NAw ²;

the following conditions are satisfied:

y≦4x−200,

y≦(4x/13)+(1000/13),

y≧4x−440, and

y≧0.

A fourth projection exposure method according to the present inventionis a projection exposure method of projecting a pattern on a projectionmaster onto a workpiece to effect exposure thereof, comprising: anillumination step of supplying exposure light of a wavelength of notmore than 200 nm to the projection master; and an image forming step offorming an image of the pattern on the projection master, at apredetermined projection magnification β on the workpiece, using aprojection optical system comprising a front lens unit, an aperturestop, and a rear lens unit; wherein the image forming step comprises afirst auxiliary step of guiding the light from the projection master tothe front lens unit, a second auxiliary step of guiding the lightpassing through the front lens unit, to the aperture stop, a thirdauxiliary step of guiding the light passing through the aperture stop,to the rear lens unit, and a fourth auxiliary step of forming the imageof the pattern on the workpiece, using the light passing through therear lens unit, wherein, where y (kg) represents a translated amount ofa first material of a disk member from an amount of the first materialamong light-transmitting optical materials in the projection opticalsystem, f2 (mm) represents a focal length of the rear lens unit, and NAwrepresents a maximum numerical aperture on the image side of theprojection optical system, and where a parameter x is defined asfollows:

x=f2 . 4|β|. NAw ²;

the following conditions are satisfied:

y≦4x−200,

y≦(4x/13)+(1000/13),

y≧4x−440, and

y≧0.

Next, a fabrication method of projection exposure apparatus according tothe present invention is a method of fabricating the fifth, sixth, orseventh projection exposure apparatus of the present invention,comprising a step of preparing an illumination optical system forsupplying exposure light of a wavelength of not more than 200 nm to theprojection master; and a step of preparing a projection optical systemfor forming an image of the pattern on the projection master, at apredetermined projection magnification β on the workpiece; wherein thestep of preparing the projection optical system comprises an auxiliarystep of preparing a front lens unit, an aperture stop, and a rear lensunit, an auxiliary step of locating the front lens unit betweenpositions where the aperture stop and the projection master are locatedrespectively, and an auxiliary step of locating the rear lens unitbetween positions where the aperture stop and the workpiece are locatedrespectively.

Next, a second microdevice fabrication method of the present inventionis a method of fabricating a microdevice having a predetermined circuitpattern, comprising: a step of projecting an image of the pattern ontothe workpiece to effect exposure thereof, using the third or fourthprojection exposure method of the present invention; and a step ofdeveloping the workpiece after the projection exposure.

Next, for accomplishing the foregoing first or second object, an eighthprojection optical system of the present invention is a dioptricprojection optical system for forming an image of a pattern on a firstsurface, on a second surface, using light of a wavelength of not morethan 200 nm, comprising: an aperture stop; a front lens unit locatedbetween the aperture stop and the first surface; and a rear lens unitlocated between the aperture stop and the second surface; wherein, wherey (kg) represents a translated amount of fluorite of a disk member froman amount of fluorite among light-transmitting optical materials in theprojection optical system, f2 (mm) a focal length of the rear lens unit,β a projection magnification of the projection optical system, and NAw amaximum numerical aperture on the image side of the projection opticalsystem, and where a parameter x is defined as follows:

x=f2 . 4|β|. NAw ²;

the following conditions are satisfied:

y≦4x−200,

y≦(4x/13)+(1000/13),

y≧4x−440, and

y≧0.

A ninth projection optical system according to the present invention isa dioptric projection optical system for forming an image of a patternof a first surface on a second surface, using light of a wavelength ofnot more than 200 nm, comprising: an aperture stop; a front lens unitlocated between the aperture stop and the first surface; and a rear lensunit located between the aperture stop and the second surface; wherein,where y (kg) represents a translated amount of a first material of adisk member from an amount of the first material amonglight-transmitting optical materials in the projection optical system,f2 (mm) represents a focal length of the rear lens unit, β a projectionmagnification of the projection optical system, and NAw represents amaximum numerical aperture on the image side of the projection opticalsystem, and where a parameter x is defined as follows:

x=f2·4|β|·NAw ²;

the following conditions are satisfied:

y≦4x−200,

y≦(4x/13)+(1000/13),

y≧4x−440, and

y≧0.

Fifth and sixth fabrication methods of a projection optical systemaccording to the present invention are methods of fabricating the eighthand ninth projection optical systems, respectively, of the presentinvention, which comprise a step of preparing a front lens unit, anaperture stop, and a rear lens unit, a step of locating the front lensunit between the aperture stop and the first surface, and a step oflocating the rear lens unit between the aperture stop and the secondsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical path diagram of a projection optical systemaccording to a first numerical example of the present invention.

FIG. 2 is an optical path diagram of a projection optical systemaccording to a second numerical example of the present invention.

FIG. 3 is lateral aberration charts of the projection optical system ofthe first numerical example.

FIG. 4 is lateral aberration charts of the projection optical system ofthe second numerical example.

FIG. 5 is a drawing to show the schematic structure of a projectionexposure apparatus according to an embodiment of the present invention.

FIG. 6 is a flowchart to show an example of microdevice fabricationmethod of the present invention.

FIG. 7 is a flowchart to show another example of microdevice fabricationmethod of the present invention.

In FIG. 8, (a) is a diagram to show the relation between parameter x andfluorite use amount y in embodiments of the fifth projection opticalsystem of the present invention, and (b) is a view to show the relationbetween a lens and a disk member.

FIG. 9 is a chart to show the relation between parameter x and useamount y of a first material in embodiments of the sixth projectionoptical system of the present invention.

FIG. 10 is an optical path diagram of a projection optical systemaccording to a third numerical example of the present invention.

FIG. 11 is an optical path diagram of a projection optical systemaccording to a fourth numerical example of the present invention.

FIG. 12 is an optical path diagram of a projection optical systemaccording to a fifth numerical example of the present invention.

FIG. 13 is an optical path diagram of a projection optical systemaccording to a sixth numerical example of the present invention.

FIG. 14 is an optical path diagram of a projection optical systemaccording to a seventh numerical example of the present invention.

FIG. 15 is lateral aberration charts of the projection optical systemaccording to the third numerical example of the present invention.

FIG. 16 is lateral aberration charts of the projection optical systemaccording to the fourth numerical example of the present invention.

FIG. 17 is lateral aberration charts of the projection optical systemaccording to the fifth numerical example of the present invention.

FIG. 18 is lateral aberration charts of the projection optical systemaccording to the sixth numerical example of the present invention.

FIG. 19 is lateral aberration charts of the projection optical systemaccording to the seventh numerical example of the present invention.

FIG. 20 is lateral aberration charts of a projection optical systemaccording to an eighth numerical example (the second numerical example)of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described withreference to the drawings. FIG. 1 and FIG. 2 are optical path diagramsof projection optical systems (which will be also referred to as“projection optical system PL”) according to examples of embodied formsof the first to seventh projection optical systems of the presentinvention.

In FIG. 1 and FIG. 2, the projection optical system PL of the presentinvention is a dioptric projection optical system for imaging a reducedimage of a pattern on a first surface A, onto a second surface B. Theprojection optical system PL has a front lens unit GF of a positiverefracting power and a rear lens unit GR of a positive refracting power.An aperture stop AS is located in the vicinity of a rear focal point ofthe front lens unit GF. The position of the aperture stop AS does notalways have to be limited to the paraxial, rear focus position of thefront lens unit GF. For example, where there exists the field curvatureof the pupil of the projection optical system PL, a vignetting (eclipse)difference can occur in the image field with change in the aperturediameter of the aperture stop AS. In order to prevent or reduce thisvignetting difference, there are also cases wherein the position of theaperture stop AS is set to a position off the paraxial, rear focal pointof the front lens unit GF (e.g., on the rear lens unit side from theparaxial, rear focal point). The aforementioned “vicinity of the rearfocal point” is thus a concept also involving such off positions. Insuch cases, the rear lens unit GR (fifth lens unit) represents anassembly of a group of lenses located from the paraxial pupil positionof the projection optical system PL to the second surface.

In the examples of FIG. 1 and FIG. 2, the aperture stop AS is locatedbetween the front lens unit GF and the rear lens unit GR.

The front lens unit GF has a first lens unit G1 of a negative refractingpower, a second lens unit G2 of a positive refracting power, a thirdlens unit G3 of a negative refracting power, and a fourth lens unit of apositive refracting power in the order named from the first surfaceside. Accordingly, the projection optical system PL of the presentinvention is also a projection optical system of a five-unitconfiguration consisting of the first lens unit G1 to fifth lens unit G5of the negative, positive, negative, positive, and positive refractingpowers.

The projection optical system PL according to the embodiments of FIG. 1and FIG. 2 is an optical system substantially telecentric on the firstsurface A side and on the second surface B side. Here “substantiallytelecentric on the first surface side and on the second surface side”means that when a ray parallel to the optical axis Ax of the projectionoptical system is made incident from the second surface B side into theprojection optical system PL, an angle between the optical axis and thisray as emitted toward the first surface, is not more than 50 minutes.

In the projection optical system of each embodiment, constructed in thisway, even if there occurs a positional deviation in the direction alongthe optical axis of a reticle (mask) as a projection master or aphotosensitive substrate (a wafer, a plate, or the like) as a workpiece,or a change of shape due to warped or the like of these projectionmaster and workpiece, it is feasible to control the magnification errorand distortion of the image due to them to a small level.

In the projection optical system of each embodiment, the followingcondition is preferably satisfied:

0.065<f2/L<0.125  (1),

where f2 represents the focal length of the rear lens unit GR (or thefifth lens unit G5) and L the distance from the first surface A to thesecond surface B (object-image distance).

The above condition (1) is a formula defined for reducing chromaticaberration of the projection optical system, particularly, axialchromatic aberration. In the range below the lower limit of Condition(1), the focal length of the rear lens unit GR (or the fifth lens unitG5) becomes too short. For this reason, the rear lens unit GR (or thefifth lens unit G5) produces extremely small quantity of axial chromaticaberration but too large monochromatic aberrations, which are toodifficult to correct, undesirably. For further satisfactory correctionof the monochromatic aberrations except for the chromatic aberration, itis preferable to set the lower limit of Condition (1) to 0.075, and forbetter correction of the monochromatic aberrations, it is morepreferable to set the lower limit of Condition (1) to 0.09.

In the range above the upper limit of Condition (1), the focal length ofthe rear lens unit GR (or the fifth lens unit G5) becomes too long. Inthis case, while the correction of the monochromatic aberrations can bemade well, the rear lens unit GR (or the fifth lens unit G5) undesirablyproduces large axial chromatic aberration. In this case, it is necessaryto narrow the wavelength band of the exposure light from the lightsource or add a refracting optical member for correction of chromaticaberration to the projection optical system PL, which is likely toincrease the loads on the light source or increase the cost of theprojection optical system PL. For further suppressing occurrence ofaxial chromatic aberration of the projection optical system, it is thuspreferable to set the upper limit of Condition (1) to 0.12.

When the exposure light is one of not more than 180 nm, only limitedkinds of radiation-transmitting refractors can transmit the exposurelight in this wavelength region and thus there is the possibility thatthe projection optical system PL itself can not be established in therange over the upper limit of Condition (1).

In the above structure, the projection optical system PL preferably hasat least one surface of aspheric shape, ASP1 to ASP6. When Condition (1)holds, it is further preferable to construct the projection opticalsystem PL so that it is provided with at least six lenses having theirrespective refracting powers and so that when six lenses are selected inorder from the first surface A side (lenses L11, L12, L21, L22, L23, andL24 in FIG. 1 and FIG. 2) of the lenses having their respectiverefracting powers, at least one surface of the six lenses is of anaspheric shape having a negative refracting power.

Describing this action, it is common practice to measure the asphericsurfaces by the Null Test using an element that makes a specificwavefront, so called a null lens or the like (which will be called a“null element”). For making a wavefront matching an aspheric surface tobe inspected, by a null element, the aspheric surface better has anegative refracting power or is concave, because it can prevent increaseof the size of the null element and increase degrees of freedom for thewavefront of the aspheric shape to be made.

If Condition (1) does not always hold, it is preferable to construct theprojection optical system PL so that it is provided with at least threelenses having their respective refracting powers and so that when threelenses are selected in order from the first surface A side (lenses L11,L12, and L21 in FIG. 1 and FIG. 2) of the lenses having their respectiverefracting powers, at least one of the three lenses is of an asphericshape having a negative refracting power. In this case, for making awavefront matching an aspheric surface to be inspected, by a nullelement for the null test, it is better for the aspheric surface to havea negative refracting power, i.e., to be concave, because it can preventthe increase of the size of the null element and increase degrees offreedom for the wavefront of the aspheric shape to be made.

As described previously, the projection optical system PL of eachembodiment has the power layout of the negative, positive, negative,positive, and positive refracting powers, and thus has the advantage oflargely decreasing the number of lenses, as compared with theconventional projection optical systems of the 6-unit configurationhaving the power layout of positive, negative, positive, negative,positive, and positive refracting powers.

In the projection optical system PL of each embodiment, let us considera composite optical system of the negative, first lens unit G1 and thepositive, second lens unit G2, and let β1 be a lateral magnification ofthis composite optical system (a composite lateral magnification of thefirst and second lens units G1, G2), L1 be a distance from the firstsurface A to the lens surface closest to the second surface B in thesecond lens unit G2, and L be a distance from the first surface A to thesecond surface B. Then the projection optical system preferablysatisfies the following conditions (2) and (3).

−1.3<1/β1<0  (2)

0.08<L1/L<0.17  (3)

The above condition (2) is a condition defined for accomplishing goodaberration correction in the entire field (the entire image field) ofthe projection optical system PL. As apparent from Condition (2), thecomposite optical system of the first and second lens units G1, G2 inthe projection optical system PL of each embodiment, converts adiverging beam from the first surface A into a slightly converging beam.

In the range below the lower limit of Condition (2), the beam convergingaction in this composite optical system G1, G2 becomes too strong, so asto increase aberration, particularly, aberration concerning angles ofview, which undesirably makes it difficult to ensure the sufficientimage field of the projection optical system PL. For further suppressingoccurrence of the aberration concerning angles of view, it is preferableto set the lower limit of Condition (2) to −1.10.

In the range above the upper limit of Condition (2) on the other hand,the negative refracting power of the first lens unit G1 becomes tooweak, so as to degrade the Petzval sum of the projection optical systemPL, which undesirably makes it difficult to ensure the sufficient imagefield of the projection optical system PL. For better correction of thePetzval sum of the projection optical system PL, it is preferable to setthe upper limit of Condition (2) to −0.42.

Condition (3) is a formula as a premise of above Condition (2) anddefines the position of the composite optical system G1, G2 of the firstand second lens units. It is preferable herein to set the lower limit ofCondition (3) to 0.1 and the upper limit of Condition (3) to 0.15.

The composite optical system G1, G2 of the first and second lens unitspreferably has at least two lens surfaces of aspheric shape, ASP1 toASP3. It is feasible to correct field curvature, distortion, sphericalaberration of pupil, etc. well by the action of the aspheric surfacesASP1 to ASP3 in this composite optical system G1, G2.

The composite optical system G1, G2 of the first and second lens unitsis preferably composed of ten or less lenses. This configuration makesit feasible to ensure the transmittance of the projection optical systemPL, reduce occurrence of flare, and decrease the cost in production.

The projection optical system PL of each embodiment preferably satisfiesthe following condition:

0.46<C/L<0.64  (4),

where C is a total thickness along the optical axis ofradiation-transmitting refractors (lenses and parallel-plane plates)located in the optical path of the projection optical system PL and Lthe distance from the first surface A to the second surface B.

The above condition (4) is a formula defined in order to achieve boththe satisfactory transmittance of the projection optical system PL andthe stable imaging performance of the projection optical system PL.

In the range below the lower limit of the above condition (4), spacingsof gas between the radiation-transmitting refractors making theprojection optical system PL become too long, so that variation in theproperties of this gas (e.g., occurrence of variation of refractiveindex due to temperature variation, pressure variation, etc., occurrenceof fluctuation, and so on) can undesirably cause variation of theimaging performance. In order to further improve the stability of theimaging performance against the environmental variations, it ispreferable to set the lower limit of Condition (4) to 0.52.

In the range over the upper limit of the above condition (4), whileimprovement is made in the resistance of the projection optical systemPL against the environmental variations, it undesirably becomesdifficult to yield the satisfactory transmittance. In order to furtherensure the satisfactory transmittance, it is preferable to set the upperlimit of Condition (4) to 0.625.

In the structure satisfying the above condition (4), the projectionoptical system PL preferably has at least one aspheric surface, ASP1 toASP6. This makes it feasible to sufficiently enhance the initial imagingperformance and ensure the satisfactory transmittance and the stabilityagainst the environmental variations.

The projection optical system PL of each embodiment preferably has atleast three lens surfaces of aspheric shape, ASP1 to ASP6. Thisstructure permits good aberration correction to be made across theentire field (the entire image field) under the configuration includingthe relatively small number of lenses (i.e., amount of glass).

It is, however, noted that it is not preferable to increase the numberof the aspheric lens surfaces ASP1 to ASP6 more than necessary, and thefollowing condition is preferably satisfied:

0.15<Ea/E<0.7  (5),

where E is the total number of members having their respectiverefracting powers (lens elements) among the radiation-transmittingrefractors in the projection optical system PL and Ea the total numberof members provided with the aspheric lens surfaces ASP1 to ASP6.

The above condition (5) is a formula for defining the optimum range ofthe number of the aspheric lens surfaces ASP1 to ASP6 in considerationof production of the projection optical system PL. The degree ofdifficulty in production of the aspheric lenses is higher than that ofspherical lenses and there are tendencies to make large eccentric errorsbetween front and back surfaces of the aspheric lenses, and large errorsof profile irregularity. Accordingly, in production of the projectionoptical system PL, it is preferable to optimize the imaging performanceof the projection optical system PL, by compensating for the errors ofthe aspheric lenses by adjusting the position and posture of thespherical lenses and adjusting the surface profiles of the sphericallenses.

In the range over the upper limit of the above condition (5), theaberration appears too large due to the errors of the aspheric lenssurfaces ASP1 to ASP6 and the number of spherical lenses is also small,so that it becomes difficult to correct the aberration due to the errorsof the aspheric surfaces ASP1 to ASP6 by the adjustment of the positionand posture and the adjustment of the profiles of the spherical lenses.For further facilitating the production of the projection optical systemPL, it is preferable to set the upper limit of Condition (5) to 0.42.

In the range below the lower limit of the above condition (5) on theother hand, while the number of the aspheric lens surfaces is small andthe production of the projection optical system PL is easy, it becomesdifficult to implement good aberration correction across the entirefield (the entire image field) and the amount of necessary glassmaterials is increased for production of the projection optical systemPL, undesirably. In order to implement better aberration correction anddecrease the amount of glass, it is preferable to set the lower limit ofCondition (5) to 0.2.

In the projection optical system PL of each embodiment, the total numberof the members having their respective refracting powers (lens elements)among the radiation-transmitting refractors making the projectionoptical system PL, is preferably not less than 16. This makes itfeasible to increase the numerical aperture on the image side (on thesecond surface B side) of the projection optical system PL and implementprojection exposure of finer patterns. When the above condition (5) ismet and when the total number of the lens elements is not less than 16,there is the advantage of ensuring the sufficient number of sphericallenses for correcting the aberration due to the errors of the asphericlenses.

In the projection optical system PL of each embodiment, the total numberof the members having their respective refracting powers (lens elements)among the radiation-transmitting refractors making the projectionoptical system PL, is preferably not more than 26. This is effective inincreasing the transmittance because of decrease in thickness of theradiation-transmitting refractors making the projection optical systemPL. In addition, it decreases the number of optical interfaces (lenssurfaces) and thus decreases losses in quantity of light at the opticalinterfaces, thus increasing the transmittance of the entire system.

In the embodiment of FIG. 1, the radiation-transmitting refractors inthe projection optical system PL are made of a single kind of material.This permits reduction in the production cost of the projection opticalsystem PL. In particular, when the projection optical system PL isoptimized for the exposure light of not more than 180 nm, the aboveconstruction is effective, because there are only limited glassmaterials with good transmittance for the exposure light in thiswavelength region.

In the embodiment of FIG. 2, the radiation-transmitting refractors inthe projection optical system PL include first radiation-transmittingrefractors made of a first material and second radiation-transmittingrefractors made of a second material. In this case, a percentage of thenumber of the second radiation-transmitting refractors to the number ofthe members having their respective refracting powers among theradiation-transmitting refractors, is preferably not more than 32%.

In particular, when the exposure light is one in the vacuum ultravioletregion of not more than 200 nm, materials are limited to some kinds ofglass materials with good transmittance for the exposure light in thiswavelength region. These glass materials also involve those requiringhigh production cost and high machining cost for formation of lens.Concerning the above high-cost glass materials, it is difficult toenhance the accuracy in processing into lenses and it is a drawback inseeking for higher accuracy of the projection optical system PL, i.e.,higher imaging performance. From this viewpoint, when the projectionoptical system PL is produced using plural kinds of glass materials andwhen the above percentage is controlled to not more than 32%, it isfeasible to achieve both reduction of production cost and improvement inthe imaging performance. The above percentage is preferably not morethan 16% and more preferably not more than 11%.

Numerical embodiments will be described below.

FIG. 1 is the optical path diagram of the projection optical system PLaccording to the first embodiment.

The projection optical system PL of the first embodiment uses thewavelength of 157.62 nm supplied from the band-narrowed F₂ laser, as areference wavelength and the chromatic aberration is corrected in therange of the wavelength band ±0.2 pm for the reference wavelength. Inthe first embodiment, all the radiation-transmitting refractors (lensesL11 to L57) in the projection optical system PL are made of fluorite(calcium fluoride, CaF₂).

As shown in FIG. 1, the projection optical system PL of the firstembodiment has the front lens unit GF of the positive refracting power,the aperture stop AS, and the rear lens unit GR of the positiverefracting power in the order named from the first surface A side.According to another grouping, the projection optical system PL of thefirst embodiment has the negative, first lens unit G1, the positive,second lens unit G2, the negative, third lens unit G3, the positive,fourth lens unit G4, the aperture stop AS, and the positive, fifth lensunit G5 in the order named from the first surface A side.

The first lens unit G1 has a negative lens L11 of the biconcave shapeand a negative lens L12 of the meniscus shape with a concave surfacefacing to the first surface A side, and these negative lenses L11, L12make a gas lens of the biconvex shape. Here the lens surface on thefirst surface A side of the negative lens L11 and the lens surface onthe second surface B side of the negative lens L12 are constructed inthe aspheric shape.

The second lens unit G2 has four positive lenses L21 to L24 of thebiconvex shape. Here the lens surface on the first surface A side of thepositive lens L24 closest to the second surface B is constructed in theaspheric shape.

The third lens unit G3 has three negative lenses L31 to L33 of thebiconcave shape and these negative lenses L31 to L33 make two gas lensesof the biconvex shape. Here the lens surface on the second surface Bside of the negative lens L33 closest to the second surface B isconstructed in the aspheric shape.

The fourth lens unit G4 has two positive lenses L41, L42 of the meniscusshape with a concave shape facing to the first surface A side, and apositive lens L43 of the biconvex shape in the order named from thefirst surface A side.

The fifth lens unit G5 has a negative lens L51 of the biconcave shape,two positive lenses L52, L53 of the biconvex shape, three positivelenses L54 to L56 of the meniscus shape with a convex surface facing tothe first surface A side, and a positive lens L57 of the planoconvexshape. Here the lens surface on the second surface B side of thepositive lens L56 is constructed in the aspheric shape.

FIG. 2 is the optical path diagram of the projection optical system PLaccording to the second embodiment.

The projection optical system PL of the second embodiment uses thewavelength of 193.306 nm supplied from the band-narrowed ArF laser, as areference wavelength and implements correction for chromatic aberrationin the range of the wavelength band ±0.4 pm for the referencewavelength. In the second embodiment, the radiation-transmittingrefractors in the projection optical system PL are made of silica glass(synthetic quartz) and fluorite.

As shown in FIG. 2, the projection optical system PL of the secondembodiment has the front lens unit GF of the positive refracting power,the aperture stop AS, and the rear lens unit GR of the positiverefracting power in the order named from the first surface A side.According to another grouping, the projection optical system PL of thefirst embodiment has the negative, first lens unit G1, the positive,second lens unit G2, the negative, third lens unit G3, the positive,fourth lens unit G4, the aperture stop AS, and the positive, fifth lensunit G5 in the order named from the first surface A side.

The first lens unit G1 has a negative lens L11 of the biconcave shapeand a negative lens L12 of the meniscus shape with a concave surfacefacing to the first surface A side, in the order named from the firstsurface A side, and these negative lenses L11, L12 make a gas lens ofthe biconvex shape. Here the lens surface on the second surface B sideof the negative lens L11 and the lens surface on the second surface Bside of the negative lens L12 are constructed in the aspheric shape.These two negative lenses L11, L12 are made both of silica glass.

The second lens unit G2 has three positive lenses L21 to L23 of thebiconvex shape and a positive lens L24 of the meniscus shape with aconvex surface facing to the first surface A side, in the order namedfrom the first surface A side. Here the lens surface on the secondsurface side of the positive lens L21 closest to the first surface A isconstructed in the aspheric shape. In the second lens unit G2, thethree, biconvex, positive lenses L21 to L23 are made of silica glass,and the positive lens L24 of the meniscus shape is of fluorite.

The third lens unit G3 has three negative lenses L31 to L33 of thebiconcave shape, and these negative lenses L31 to L33 make two gaslenses of the biconvex shape. Here the lens surface on the first surfaceA side of the negative lens L33 closest to the second surface B isconstructed in the aspheric shape. All the negative lenses L31 to L33 inthe third lens unit G3 are made of silica glass.

The fourth lens unit G4 has a positive lens L41 of the meniscus shapewith a concave shape facing to the first surface A side, a positive lensL42 of the planoconvex shape with a convex surface facing to the secondsurface B side, and a positive lens L43 of the meniscus shape with aconvex surface facing to the first surface A side, in the order namedfrom the first surface A side. Here the three positive lenses L41 to L43are made all of silica glass.

The fifth lens unit G5 has a negative lens L51 of the meniscus shapewith a convex surface facing to the first surface A side, a positivelens L52 of the biconvex shape, four positive lenses L53 to L56 of themeniscus shape with a convex surface facing to the first surface A side,and a negative lens L57 of the planoconcave shape with a concave surfacefacing to the first surface A side, in the order named from the firstsurface A side. Here the lens surface on the second surface B side ofthe negative lens L51 of the meniscus shape and the lens surface on thesecond surface side of the positive lens L56 of the meniscus shape areconstructed in the aspheric shape. In the fifth lens unit G5, thepositive lens L52 of the biconvex shape is made of fluorite and the restlenses L51, L53 to L57 are of silica glass.

When the silica glass (synthetic quartz) and fluorite are used as lensmaterials (glass materials), as in the case of the projection opticalsystem PL of the second embodiment, the lens surfaces of the asphericshape are preferably formed in the lenses of silica glass.

Table 1 and Table 2 below provide the specifications of the projectionoptical system PL of the first and second embodiments. In Table 1 andTable 2, the left end column indicates numbers of the respective lenssurfaces from the first surface A, the second column radii of curvatureof the respective lens surfaces, the third column surface spacings fromeach lens surface to a next lens surface, the fourth column lensmaterials, the fifth column symbols of the aspheric surfaces, and thesixth column symbols of the respective lenses. A radius of curvature inthe second column for each aspheric lens surface represents a radius ofcurvature at a vertex thereof. In Table 2, φ_(eff) represents a clearaperture diameter of each lens surface.

The aspheric shape is expressed by Eq. (a) below. $\begin{matrix}\begin{matrix}{{Z(Y)} = \quad {\frac{Y^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right){Y^{2}/r^{2}}}}} +}} \\{\quad {{AY}^{4} + {BY}^{6} + {CY}^{8} + {DY}^{10} + {EY}^{12} + {FY}^{14}}}\end{matrix} & (a)\end{matrix}$

Y: height from the optical axis

z: distance along the direction of the optical axis from a tangent planeat the vertex of each aspheric surface to the aspheric surface

r: radius of curvature at the vertex

κ: conical coefficient

A, B, C, D, E, F: aspheric coefficients

In the last part of Table 1 and Table 2 there are presented the conicalcoefficient κ and the aspheric coefficients A, B, C, D, E, F for eachaspheric surface as [aspheric data].

The projection optical system of the first embodiment uses fluorite asthe lens material (glass material) and the second embodiment silicaglass (synthetic quartz) and fluorite.

The refractive index of fluorite at the reference wavelength (157.62 nm)of the first embodiment is 1.5593067 and a change of refractive indexper the wavelength+1 pm (dispersion) is −2.6×10⁻⁶.

In the second embodiment the refractive index of silica glass (syntheticquartz) at the reference wavelength (193.306 nm) is 1.5603261, and achange of refractive index per the wavelength+1 pm (dispersion) is−1.59×10⁻⁶. Further, the refractive index of fluorite at the referencewavelength (193.306 nm) is 1.5014548 and a change of refractive indexper the wavelength+1 pm (dispersion) is −0.98×10⁻⁶.

In Table 1 and Table 2 below, SiO₂ represents silica glass, CaF₂represents fluorite, d0 represents the distance from the first surface Ato the surface closest to the first surface A, WD represents thedistance from the surface closest to the second surface B, to the secondsurface B (workpieceing distance), β represents the projectionmagnification, NA represents the numerical aperture on the secondsurface B side, and φ represents the diameter of the image circle on thesecond surface B.

TABLE 1 First Embodiment (FIG. 1) d0 = 40.6446 (mm) WD = 10.8134 (mm) |β | = 1/4 NA = 0.75 Ø = 23 (mm) Radius of Surface curvature distanceAspheric (mm) (mm) Glass surface Lens  1: −446.6132 12.0000 CaF₂ ASP1L11  2: 554.7232 22.5800  3: −92.3259 46.8618 CaF₂ L12  4: −6695.39731.1105 ASP2  5: 3832.9930 50.0000 CaF₂ L21  6: −179.0867 2.1599  7:552.3099 44.4615 CaF₂ L22  8: −337.8904 72.3130  9: 416.2197 34.5857CaF₂ L23 10: −885.0528 1.0000 11: 179.8393 45.7388 CaF₂ ASP3 L24 12:−3356.1983 59.3145 13: −4096.8404 12.0000 CaF₂ L31 14: 160.6568 14.583315: −317.8664 12.0000 CaF₂ L32 16: 146.7839 35.8889 17: −96.9946 12.8163CaF₂ L33 18: 190.5253 13.5021 ASP4 19: −335.6495 50.0000 CaF₂ L41 20:−220.3094 1.0000 21: −2196.6594 26.1615 CaF₂ L42 22: −200.6039 62.731723: 245.0000 38.2977 CaF₂ L43 24: −522.0290 1.0000 25: ∞ 17.3237 AS 26:−268.6720 20.2571 CaF₂ L51 27: 312.7719 6.2767 ASP5 28: 421.1502 30.5995CaF₂ L52 29: −570.5232 1.0000 30: 392.6194 38.7693 CaF₂ L53 31:−392.6194 18.3534 32: 208.4943 34.4190 CaF₂ L54 33: 993.1946 13.7466 34:100.1780 50.0000 CaF₂ L55 35: 182.3029 1.4636 36: 100.1446 20.5148 CaF₂L56 37: 166.7499 6.9737 ASP6 38: 23871.5667 36.7374 CaF₂ L57 39: ∞ (WD)[Aspheric Data] ASP1 κ: 0.000000 A: 0.193140 × 10⁻⁶ B: −0.824604 × 10⁻¹¹C: 0.290280 × 10⁻¹⁵ D: −0.163368 × 10⁻¹⁹ E: −0.748150 × 10⁻²³ F:0.191873 × 10⁻²⁶ ASP2 κ: 0.000000 A: 0.489084 × 10⁻⁷ B: −0.220485 ×10⁻¹¹ C: 0.962305 × 10⁻¹⁶ D: −0.287934 × 10⁻²⁰ E: 0.318426 × 10⁻²⁵ F:0.736564 × 10⁻³⁰ ASP3 κ: 0.000000 A: −0.350067 × 10⁻⁸ B: −0.254455 ×10⁻¹² C: −0.464126 × 10⁻¹⁷ D: −0.307104 × 10⁻²¹ E: −0.247414 × 10⁻²⁷ F:−0.475856 × 10⁻³⁰ ASP4 κ: 0.000000 A: 0.103662 × 10⁻⁶ B: −0.141741 ×10⁻¹⁰ C: 0.495429 × 10⁻¹⁵ D: 0.567158 × 10⁻¹⁹ E: −0.655441 × 10⁻²³ F:0.227245 × 10⁻²⁷ ASP5 κ: 0.000000 A: 0.166512 × 10⁻⁷ B: 0.572516 × 10⁻¹³C: −0.931419 × 10⁻¹⁷ D: −0.141990 × 10⁻²¹ E: 0.347373 × 10⁻²⁶ F:−0.357575 × 10⁻³¹ ASP6 κ: 0.000000 A: −0.827300 × 10⁻⁸ B: −0.150446 ×10⁻¹⁰ C: −0.119559 × 10⁻¹⁴ D: −0.367677 × 10⁻¹⁹ E: 0.140360 × 10⁻²² F:0.443761 × 10⁻²⁶

TABLE 2 Second Embodiment (FIG. 2) d0 = 50.2691 (mm) WD = 12.7196 (mm) |β | = 1/4 NA = 0.75 Ø = 26.6 (mm) Radius of curvature Spacing AsphericØ_(eff) (mm) (mm) Glass surface Lens (mm)  1: −310.0151 14.1998 Si0₂ L1161.615337  2: 303.6996 31.5711 ASP1 66.565666  3: −100.7999 43.9802 Si0₂L12 66.983185  4: −223.9596 9.5226 ASP2 93.367592  5: 723.6127 40.8525Si0₂ L21 116.401726  6: −326.4452 1.4173 ASP3 120.452324  7: 1771.097146.9449 Si0₂ L22 127.712166  8: −289.4624 104.4363 129.745331  9:315.8237 54.1717 Si0₂ L23 129.661499 10: −982.0234 5.9069 126.792755 11:177.1899 46.2445 CaF₂ L24 109.210121 12: 2145.8394 52.0242 103.95140113: −383.7553 14.4116 Si0₂ L31 70.429657 14: 103.2214 24.7417 57.78972615: −406.0024 33.8665 Si0₂ L32 57.333916 16: 264.3030 20.2564 55.37033817: −130.6551 36.7937 Si0₂ ASP4 L33 55.433979 18: 243.2466 22.757168.153618 19: −214.9802 30.3809 Si0₂ L41 69.129860 20: −138.6461 1.672078.097023 21: ∞ 21.7611 Si0₂ L42 88.842262 22: −503.4971 3.213392.214386 23: 300.0000 39.0994 Si0₂ L43 100.787971 24: 1276.4893 64.3575101.914116 25: ∞ 17.6348 AS 107.438789 26: 634.9754 23.4375 Si0₂ L51112.544273 27: 428.5036 1.0000 ASP5 114.046783 28: 374.4189 48.2150 CaF₂L52 114.698341 29: −377.2840 5.8246 115.519508 30: 312.6914 30.9155 Si0₂L53 115.577393 31: 1319.1903 24.0395 113.770447 32: 272.3437 35.8174Si0₂ L54 107.279770 33: 2421.5392 21.5533 103.251373 34: 111.238935.3044 Si0₂ L55 82.084534 35: 217.9576 8.7809 74.716202 36: 117.876224.0827 Si0₂ L56 63.873623 37: 206.3743 8.3992 ASP6 55.041325 38:−4906.7588 47.4235 Si0₂ L57 53.879700 39: ∞ (WD ) 27.722666 [AsphericData] ASP1 κ: 0.000000 A: −0.140916 × 10⁻⁶ B: 0.565597 × 10⁻¹¹ C:−0.301261 × 10⁻¹⁵ D: −0.207339 × 10⁻¹⁹ E: 0.554668 × 10⁻²³ F: −0.585529× 10⁻²⁷ ASP2 κ: 0.000000 A: 0.319500 × 10⁻⁸ B: −0.616429 × 10⁻¹² C:−0.170315 × 10⁻¹⁶ D: 0.486911 × 10⁻²⁰ E: −0.144218 × 10⁻²⁴ F: 0.926412 ×10⁻²⁹ ASP3 κ: 0.000000 A: 0.263695 × 10⁻⁷ B: 0.676253 × 10⁻¹² C:−0.828213 × 10⁻¹⁷ D: −0.121949 × 10⁻²⁰ E: 0.572412 × 10⁻²⁵ F: −0.806708× 10⁻³⁰ ASP4 κ: 0.000000 A: −0.879103 × 10⁻⁷ B: 0.950068 × 10⁻¹² C:0.184679 × 10⁻¹⁵ D: 0.197968 × 10⁻¹⁹ E: 0.107088 × 10⁻²³ F: −0.173148 ×10⁻²⁷ ASP5 κ: 0.000000 A: 0.401293 × 10⁻⁸ B: 0.300603 × 10⁻¹² C:−0.310130 × 10⁻¹⁷ D: 0.269304 × 10⁻²² E: −0.108809 × 10⁻²⁷ F: 0.341338 ×10⁻³² ASP6 κ: 0.000000 A: −0.141220 × 10⁻⁷ B: −0.760266 × 10⁻¹¹ C:−0.429061 × 10⁻¹⁵ D: 0.179175 × 10⁻²⁰ E: 0.705845 × 10⁻²³ F: −0.321978 ×10⁻²⁷ ASP4 κ: 0.000000 A: −0.879103 × 10⁻⁷ B: 0.950068 × 10⁻¹² C:0.184679 × 10⁻¹⁵ D: 0.197968 × 10⁻¹⁹ E: 0.107088 × 10⁻²³ F: −0.173148 ×10⁻²⁷ ASP5 κ: 0.000000 A: 0.401293 × 10⁻⁸ B: 0.300603 × 10⁻¹² C:−0.310130 × 10⁻¹⁷ D: 0.269304 × 10⁻²² E: −0.108809 × 10⁻²⁷ F: 0.341338 ×10⁻³² ASP6 κ: 0.000000 A: −0.141220 × 10⁻⁷ B: −0.760266 × 10⁻¹¹ C:−0.429061 × 10⁻¹⁵ D: 0.179175 × 10⁻²⁰ E: 0.705845 × 10⁻²³ F: −0.321978 ×10⁻²⁷

Now numerals corresponding to the conditions in the respectiveembodiments are presented in Table 3 below.

TABLE 3 f 2/L 1/β 1 L1/L C/L E a/E (1) (2) (3) (4) (5) Embodiment 10.108 −0.74 0.120 0.604 0.316 Embodiment 2 0.111 −0.88 0.121 0.576 0.316

As shown in Table 3 above, the first and second embodiments both satisfythe foregoing conditions.

Next, FIG. 3 and FIG. 4 show the lateral aberration charts on the secondsurface B of the projection optical system PL according to the first andsecond embodiments, respectively.

FIG. 3(A) is a lateral aberration chart in the meridional direction atthe image height Y=11.5, FIG. 3(B) a lateral aberration chart in themeridional direction at the image height Y=5.75, FIG. 3(C) a lateralaberration chart in the meridional direction at the image height Y=0 (onthe optical axis), FIG. 3(D) a lateral aberration chart in the sagittaldirection at the image height Y=11.5, FIG. 3(E) a lateral aberrationchart in the sagittal direction at the image height Y=5.75, and FIG.3(F) a lateral aberration chart in the sagittal direction at the imageheight Y=0 (on the optical axis). In each of the lateral aberrationcharts of FIG. 3(A) to FIG. 3(F), a solid line represents an aberrationcurve at the wavelength λ=157.62 nm (reference wavelength), a dashedline an aberration curve at the wavelength λ=157.62 nm+0.2 pm (referencewavelength+0.2 pm), and a chain line an aberration curve at thewavelength λ=157.62 nm−0.2 pm (reference wavelength−0.2 pm).

FIG. 4(A) is a lateral aberration chart in the meridional direction atthe image height Y=13.3, FIG. 4(B) a lateral aberration chart in themeridional direction at the image height Y=6.65, FIG. 4(C) a lateralaberration chart in the meridional direction at the image height Y=0 (onthe optical axis), FIG. 4(D) a lateral aberration chart in the sagittaldirection at the image height Y=13.3, FIG. 4(E) a lateral aberrationchart in the sagittal direction at the image height Y=6.65, and FIG.4(F) a lateral aberration chart in the sagittal direction at the imageheight Y=0 (on the optical axis). In each of the lateral aberrationcharts of FIG. 4(A) to FIG. 4(F), a solid line represents an aberrationcurve at the wavelength λ=193.306 nm (reference wavelength), a dashedline an aberration curve at the wavelength λ=193.306 nm+0.4 pm(reference wavelength+0.4 pm), and a chain line an aberration curve atthe wavelength λ=193.306 nm−0.4 pm (reference wavelength−0.4 pm).

As apparent from FIG. 3, in the projection optical system PL of thefirst embodiment, excellent correction for chromatic aberration isachieved across the wavelength region of ±0.2 pm, though the system isconstructed using only the single kind of glass material, in thewavelength region of not more than 180 nm.

As also apparent from FIG. 4, in the projection optical system PL of thesecond embodiment, excellent correction for chromatic aberration isachieved across the wavelength region of ±0.4 pm, though the system isconstructed using only the small number of lens elements for correctionof chromatic aberration (approximately 10% of all the lens elements), inthe vacuum ultraviolet wavelength region of not more than 200 nm.

The projection optical system PL of the first embodiment has thecircular image field having the diameter of 23 mm and can ensure therectangular exposure region having the width of 6.6 mm in the scanningdirection and the width of 22 mm in the direction perpendicular to thescanning direction, in the image field. The projection optical system PLof the second embodiment has the circular image field having thediameter of 26.6 mm and can ensure the rectangular exposure regionhaving the width of 8.8 mm in the scanning direction and the width of 25mm in the direction perpendicular to the scanning direction, in theimage field.

In the next place, examples of preferred forms of the eighth and ninthprojection optical systems according to the present invention will bedescribed below. FIG. 10 to FIG. 14 are the optical path diagrams of theprojection optical systems according to the embodiments of the eighthand ninth projection optical systems of the present invention. It is,however, noted that the projection optical systems of FIG. 1 and FIG. 2described above can be included in the embodiments of the eighth andninth projection optical systems of the present invention in certaincases, as described hereinafter.

In FIG. 10 to FIG. 14, the projection optical systems of the examples(which will be also referred to hereinafter as “projection opticalsystem PL”) are dioptric projection optical systems for forming areduced image of a pattern on the first surface A, onto the secondsurface B. When these projection optical systems are applied, forexample, to the projection exposure apparatus for fabrication ofsemiconductor devices, a pattern surface of reticle R as a projectionmaster (mask) is placed on the first surface A, and a photoresistcoating surface (exposure surface) of wafer W being a substrate to beexposed as a workpiece, is placed on the second surface B. Theprojection optical systems have a front lens unit GF of a positiverefracting power, a rear lens unit GR of a positive refracting power,and an aperture stop AS in the vicinity of a rear focal point of thefront lens unit GF. The position of the aperture stop AS does not alwayshave to be limited to the paraxial, rear focal point of the front lensunit GF. This is similar to the cases of the embodiments of FIG. 1 andFIG. 2. In this case, the rear lens unit GR represents an assembly of agroup of lenses located from the paraxial pupil position of theprojection optical system to the second surface B.

In the examples of FIG. 10 to FIG. 14, the aperture stop AS is locatedbetween the front lens unit GF and the rear lens unit GR.

The projection optical systems in the examples of FIG. 10 to FIG. 14 areoptical systems that are substantially telecentric on the first surfaceA side and on the second surface B side, as in the case of the examplesof FIG. 1 and FIG. 2. As a result, in the projection optical systems ofthe examples, even if there occurs the positional deviation in thedirection of the optical axis of the reticle (mask) as a projectionmaster or the photosensitive substrate (wafer, plate, or the like) as aworkpiece, or the profile change due to warped or the like of theseprojection master and workpiece, it is also feasible to decrease themagnification error and distortion of images due to them.

In the projection optical system according to an embodiment of theeighth projection optical system (the fifth projection exposureapparatus or the third projection exposure method) of the presentinvention, the exposure light is one having the wavelength of not morethan 200 nm and, letting y (kg) be a translated amount of fluorite of adisk member from an amount (use amount) of fluorite (CaF₂) among theradiation transmitting optical materials in the projection opticalsystem, f2 (mm) be the focal length of the rear lens unit GR, and NAw bean image-side maximum numerical aperture of the projection opticalsystem, a parameter x (mm) is defined as follows.

x=f2 . 4|β|. NAw ²  (10)

In this case, as shown in FIG. 8(b), a disk member D of a lens L used inthe projection optical system is a cylindrical member used infabrication of the lens L. When r_(eff) represents an effective radius(a radius of clear aperture) of the lens L (the larger of those on theentrance side and on the exit side) and dS a holding width for stablyholding the lens L, a radius r_(d) of the disk member D is given by(r_(eff)+dS) and the length of the disk member D by a length of acylinder circumscribed about the lens L. Accordingly, the translatedamount y of fluorite of the disk member from the use amount of fluoriteconsequently represents the total amount of fluorite used in fabricationof the projection optical system.

In the present example the holding width dS is 8 mm. Under thesecircumstances, the optical system of the example is configured tosatisfy the following conditions.

y≦4x−200  (11)

y≦(4x/13)+(1000/13)  (12)

y≧4x−440  (13)

y≧0  (14)

FIG. 8(a) shows the relation between the parameter x and the fluoriteamount y (the use amount reduced to the disk member) in the embodimentof the present invention, and in this FIG. 8(a), straight lines B1, B2,B3, and B4 indicate a line (y=4x−200), a line (y=(4x/13)+(1000/13)), aline (y=4x−440), and a line (y=0), respectively. The range of (x, y)satisfying the conditions of Eq (11) to Eq (14) consequently is therectangular region B5 surrounded by the lines B1, B2, B3, B4 of FIG.8(a).

The chromatic aberration of optical system is usually corrected byadequately combining optical materials of different dispersions(conventional correction technique). However, when the exposure light islight in the wavelength region of not more than 200 nm (vacuumultraviolet radiation) as in the present example, optical materials(light-transmitting optical materials) for the lenses (including theparallel-plane plates for correction of aberration and the like)transmitting the exposure light are limited in kind. Specifically,practically applicable materials for the combination of plural opticalmaterials of mutually different dispersions in the wavelength region ofapproximately 170 to 200 nm are silica glass (synthetic quartz) andfluorite. Since fluorite is produced in the small volume of productionand is expensive, it is desirable to decrease the use amount y offluorite to as low as possible in order to decrease the production costof the projection optical system and eventually decrease the productioncost of the projection exposure apparatus provided therewith.

Then the inventor considered applying the technique of correcting thechromatic aberration for the light with predetermined wavelength band byproportional reduction of the optical system (correction technique byproportional reduction), to the optical system of the instant example,and found that, in order to correct the chromatic aberration well whilereducing the amount of fluorite y for the light of the wavelength of notmore than 200 nm as much as possible, the region B5 of FIG. 8(a) was theoptimum combination of the foregoing conventional correction technique(capable of control by the amount of fluorite y) with the correctiontechnique by proportional reduction (capable of control by the parameterx).

When Condition (11) is not satisfied, i.e., in the region B1 e above theline B1, the focal length f2 of the rear lens unit GR is too shortagainst the amount y of fluorite. In this case, the power of the entireprojection optical system is too strong and it is difficult to correcteven the monochromatic aberrations. Thus this region is not preferable.In other words, fluorite is used more than necessary against the focallength f2 of the rear lens unit GR. Namely, the chromatic aberrationcorrection by the technique of proportional reduction is not effected somuch, and the use amount of fluorite is undesirably increasedfruitlessly.

When Condition (12) is not met, i.e., in the region B2 e above the lineB27, the absolute use amount of fluorite is undesirably increased.

When Condition (13) is not met, i.e., in the region B3 e outside theline B3, it becomes easier to correct the monochromatic aberrations ofthe projection optical system, but the correction of chromaticaberration becomes largely insufficient, so as to degrade the imagingperformance, undesirably. Since the amount y of fluorite is 0 or apositive value, Condition (14) is always satisfied.

In the present embodiment, the image-side maximum numerical aperture NAwof the projection optical system and the fluorite amount y (the reduceduse amount to the disk member) are preferably set to further satisfy thefollowing two conditions.

NAw>0.72  (d-1)

y<75  (d-2)

When Condition (d-1) is not satisfied, it is not feasible to yield asatisfactory resolution. Further, since the volume production offluorite is difficult at present, when Condition (d-2) is not met, thereis the possibility that it becomes difficult to increase the supply ofprojection optical systems PL (and the projection exposure apparatusequipped therewith) according to demands.

In the present embodiment, the focal length f2 (mm) of the rear lensunit GR and the image-side maximum numerical aperture NAw of theprojection optical system are desirably set to satisfy the followingcondition.

 110<f2/NAw<200  (e)

When the value of f2/NAw is not more than the lower limit of Condition(e), it becomes difficult to correct off-axial aberrations such as coma,astigmatism, and distortion. When the value of f2/NAw is not less thanthe upper limit of Condition (e), it becomes difficult to correct thechromatic aberration.

In order to further decrease the fluorite amount y and well correct thechromatic aberration by proportional reduction, it is desirable tosatisfy the following conditions (15) to (18), which are narrowerconditions than Conditions (11) to (14).

y≦(9x/2)−270  (15)

y≦90  (16)

y≧(9x/2)−(855/2)  (17)

y≧0  (18)

In FIG. 8(a), straight lines C1, C2, C3, and C4 indicate a line(y=(9x/2)−270), a line (y=90), a line (y=(9x/2)−(855/2)), and a line(y=0), respectively. Accordingly, the range of (x, y) satisfyingConditions (15) to (18) is the rectangular region C5 surrounded by thelines C1, C2, C3, C4 and this region C5 is in the range of the regionB5.

The exposure light is desirably one having the wavelength of not morethan 200 nm and the wavelength band having the full width at halfmaximum of not more than 0.5 pm. As the wavelength band becomesnarrower, it becomes easier to correct the chromatic aberration, but thestructure of the exposure light source becomes more complex accordingthereto, so as to increase the production cost and inevitably decreasethe exposure dosage, thus lowering the throughput. When the exposurelight source is, for example, an ArF excimer laser source (thewavelength 193 nm), the wavelength bands of not more than 0.5 pm toapproximately 0.3 pm are bands that can be realized at reasonable costby the band narrowing technique and the chromatic aberration can also bereadily corrected by the correction technique of the present example.

In the present example, the correction technique by proportionalreduction is applied and, in order to ensure the wide field whilecontrolling the various aberrations on the image plane side to withinpermissible ranges on this occasion, it is desirable to employ asphericsurfaces for predetermined lens surfaces of lenses of a plurality oflenses making the projection optical system. However, since theproduction cost of aspheric lenses is high, it is desirable to minimizethe number of aspheric surfaces within the range permitting the desiredimaging performance.

In the present example, Conditions (11) to (14) are satisfied, and whenthe following condition about the fluorite amount y is further imposed,the number A of aspheric surfaces in the projection optical system isdesirably not less than 2.

0≦y<40  (19)

2≦A  (20)

Describing this further, since the fluorite amount y is relatively smallwithin the range of Condition (19), the focal length f2 of the rear lensunit GR is set to a relatively short value from Conditions (11) to (14).Namely, the chromatic aberration correction by proportional reductiontends to become dominant. In this case, if the number of asphericsurfaces is smaller than 2, the range of the image field well correctedfor aberration becomes too narrow and it will lead to decrease ofthroughput when applied to the projection exposure apparatus. It is thusdesirable to use two or more aspheric surfaces in order to implementgood aberration correction in the desired range of image field. In orderto effect good aberration correction in a wider image field, the numberof aspheric surfaces is more preferably not less than three.

When the following condition different from Condition (19) is imposed asto the fluorite amount y, the number A of aspheric surfaces in theprojection optical system is desirably 1 to 5.

40≦y<70  (21)

1≦A≦5  (22)

In the range of this condition (21), because of increase in the fluoriteamount y, the focal length f2 of the rear lens unit GR can be set longerfrom Conditions (11) to (14) than in the case of the range of Condition(19). Namely, since the chromatic aberration correction by proportionalreduction is made in addition to the correction technique of combiningplural materials, use of aspheric surfaces in the number of not lessthan 1 nor more than 5 permits the aberration to be corrected wellwithin the desired range of image field. When no aspheric surface isused off Condition (22), it becomes difficult to maintain theproportionally reduced image field in the state before the proportionalreduction, which is undesirable. When there are aspheric surfaces overfive surfaces, the production cost is undesirably increased more thannecessary.

For providing the projection optical system with an aspheric surface,this aspheric surface is desirably provided in a lens surface of a lensmade of a material (e.g., silica glass) different from fluorite. If theaspheric surface is provided in a lens of fluorite to the contrary, itwill be difficult to process fluorite into an aspheric surface becauseof great abrasion of fluorite and it can cause considerable increase ofproduction cost and production time and further degrade the accuracy ofaspheric surface.

The image field of the projection optical system in the present exampleis desirably not less than 20 mm in diameter (more desirably, not lessthan 25 mm in diameter), and the image-side maximum numerical apertureNAw of the projection optical system is desirably set to satisfy thefollowing condition.

NAw≧0.65  (23)

Using the exposure wavelength λ, the maximum numerical aperture NAw, andthe process coefficient k1, the resolution Res of the image to betransferred by the projection optical system is given as follows.

Res=k1·λ/NAw  (24)

Accordingly, supposing the exposure wavelength λ is 200 nm, the maximumnumerical aperture NAw 0.65, and, for example, on the assumption ofapplication of the modified illumination method, the process coefficientk1 0.5, the resolution Res is about 154 nm. Therefore, when Condition(23) is satisfied at the exposure wavelength of not more than 200 nm, itis feasible to yield the resolution enough for fabrication ofnext-generation semiconductor devices and the like.

When the diameter of the image field is not less than 20 mm, exposurecan be implemented at high throughput in the state of high resolution.

In the projection optical system according to an embodiment of the ninthprojection optical system (the sixth projection exposure apparatus orthe fourth projection exposure method) of the present invention, theexposure light is one having the wavelength of not more than 200 nm andy (kg) represents a translated amount of a first material of a diskmember from an amount (use amount) of the first material among theradiation transmitting optical materials in the projection opticalsystem. Then Conditions (11) to (14) are satisfied where the focallength of the rear lens unit GR is f2 (mm), the image-side maximumnumerical aperture of the projection optical system is NAw, and theparameter x (mm) is defined as in Eq (10).

FIG. 9 shows the relation between the parameter x (mm) and the amount y(the use amount reduced to the disk member) (kg) of the first materialin this embodiment, wherein the straight lines B1 to B4 and the straightlines C1 to C4 in this FIG. 9 are the same as those in FIG. 8(a) and theregion satisfying Conditions (11) to (14) is the region B5 surrounded bythe lines B1 to B4.

In this embodiment of FIG. 9, a second material different from the firstmaterial is first used as a principal material (light-transmittingoptical material) for the lenses making the projection optical system,and then the first material is added according to the necessity forcorrection of chromatic aberration. The present embodiment further usesa correction technique of effecting achromatism by proportionallyreducing the optical system. Namely, the present example can be said tobe “an example of finding the range of optimum combination of thecorrection technique by proportional reduction with the correctiontechnique of achromatism by adding the chromatic-aberration-correctingmaterial (first material) to the principal material (second material).”

In the present example, not only silica, but also fluorite and the likecan be used as the principal material (second material). When theprincipal material is, for example, silica, the first material can beselected from fluorite (which corresponds to the embodiment of FIG.8(a)), barium fluoride (BaF₂), lithium fluoride (LiF), and so on. On theother hand, for example, at the exposure wavelengths of not more than170 nm (e.g., the F₂ laser of the wavelength of 157 nm), it is alsoconceivable to use fluorite as the principal material in order toincrease the transmittance, and in this case the first material isselected from materials (silica, BaF, LiF, etc.) different fromfluorite.

In FIG. 9, when Condition (11) is not satisfied, it can be mentionedthat the first material is used more than necessary against the focallength f2 of the rear lens unit GR. When Condition (12) is notsatisfied, the absolute use amount of the second material becomes largeand the transmittance becomes too low, for example, at the exposurewavelengths of not more than 170 nm, undesirably.

When Condition (13) is not satisfied, it becomes easier to correct themonochromatic aberrations of the projection optical system, but thecorrection of chromatic aberration becomes largely insufficient, so asto degrade the imaging performance, undesirably.

In the present example, it is desirable to satisfy Conditions (d-1),(d-2), in order to obtain the satisfactory resolution and control theuse amount of fluorite to within the practical range. It is alsodesirable to satisfy Condition (e), in order to readily correct theoff-axial aberrations such as coma, astigmatism, and distortion andreadily correct the chromatic aberration.

In the present example, in order to further decrease the amount y of thefirst material and correct the chromatic aberration well by proportionalreduction, it is also desirable to satisfy the above conditions (15) to(18), which are narrower conditions than Conditions (11) to (14). Thisis the case wherein (x, y) is in the region C5 surrounded by the linesC1 to C4 of FIG. 9.

In FIG. 9, data A1 corresponds to the foregoing first embodiment. In thefirst embodiment, the exposure wavelength is 157 nm of the F₂ laser(note more than 170 nm), all the lenses are made of the same material(second material) of silica, and the amount y of the first material is0. In the first embodiment, the focal length f2 of the rear lens unit GRis 110.6 mm, the projection magnification β−0.25, and the image-sidemaximum numerical aperture Naw 0.75. Therefore, the parameter x=110.6 .4 . |−0.25|. 0.75²=62.2 (mm), so that the data A1 is in the moredesirable region C5.

A plurality of numerical embodiments of the present example will bedescribed below. The projection optical systems of the third embodimentto the eighth embodiment below all use the wavelength of 193.3 nmsupplied from the band-narrowed ArF laser as the reference wavelengthand the chromatic aberration is corrected in the range of FWHM (fullwidth at half maximum) of 0.35 pm centered about the referencewavelength, i.e., in the range of 193.3 nm±0.175 pm.

FIG. 10 is the optical path diagram of the projection optical systemaccording to the third embodiment. In this third embodiment, all theradiation-transmitting refractors (lenses L11 to L57) in the projectionoptical system are made of silica (synthetic quartz: SiO₂). Namely, thematerial for achromatism (the first material) is not used.

As shown in FIG. 10, the projection optical system of the thirdembodiment has the front lens unit GF of the positive refracting power,the aperture stop AS, and the rear lens unit GR of the positiverefracting power in the order named from the first surface A side.According to another grouping, the projection optical system of thethird embodiment has the negative, first lens unit G1, the positive,second lens unit G2, the negative, third lens unit G3, the positive,fourth lens unit G4, the aperture stop AS, and the positive, fifth lensunit G5 in the order named from the first surface A side, in which thefirst lens unit G1 to the fourth lens unit G4 constitute the front lensunit GF and the fifth lens unit G5 the rear lens unit GR.

The first lens unit G1 has a negative lens L11 of the meniscus shapewith a convex surface facing to the first surface A side, and a negativelens L12 of the meniscus shape with a concave surface facing to thefirst surface A side in the order named from the first surface A side,and these negative lenses L11, L12 form a gas lens of the biconvexshape. The lens surface on the first surface A side of the negative lensL11 and the lens surface on the second surface B side of the negativelens L12 are formed as aspheric surfaces ASP1 and ASP2, respectively.

The second lens unit G2 has a negative lens L21 of the meniscus shapewith a concave surface facing to the first surface A side, a positivelens L22 of the meniscus shape with a concave surface facing to thefirst surface A side, and three positive lenses L23 to L25 of thebiconvex shape. The lens surface on the first surface A side of thepositive lens L25 closest to the second surface B is formed as anaspheric surface ASP3.

The third lens unit G3 has a negative lens L31 of the meniscus shapewith a convex surface facing to the first surface A side, and twonegative lenses L32, L33 of the biconcave shape in the order named fromthe first surface A side, and these negative lenses L31 to L33 form twogas lenses of the biconvex shape. The lens surface on the second surfaceB side of the negative lens L33 closest to the second surface B isformed as an aspheric surface ASP4.

The fourth lens unit G4 has two positive lenses L41, L42 of the meniscusshape with a concave surface facing to the first surface A side and apositive lens L43 of the biconvex shape in the order named from thefirst surface A side.

The fifth lens unit G5 also being the rear lens unit GR, has a negativelens L51 of the biconcave shape, two positive lenses L52, L53 of thebiconvex shape, three positive lenses L54 to L56 of the meniscus shapewith a convex surface facing to the first surface A side, and a negativelens L57 of the planoconcave shape with a concave surface facing to thefirst surface A side, in the order named from the first surface A side.Here the lens surface on the first surface A side of the positive lensL52 and the lens surface on the second surface B side of the positivelens L56 are formed as aspheric surfaces ASP5 and ASP6, respectively.

FIG. 11 is the optical path diagram of the projection optical systemaccording to the fourth embodiment. In this fourth embodiment, silicaglass (synthetic quartz) is used as the principal material (secondmaterial) of the radiation-transmitting refractors in the projectionoptical system and fluorite as the achromatizing material (firstmaterial).

As shown in FIG. 11, the projection optical system of the fourthembodiment has the front lens unit GF of the positive refracting power,the aperture stop AS, and the rear lens unit GR of the positiverefracting power in the order named from the first surface A side.According to another grouping, the projection optical system PL of thefourth embodiment has the negative, first lens unit G1, the positive,second lens unit G2, the negative, third lens unit G3, the positive,fourth lens unit G4, the aperture stop AS, and the positive, fifth lensunit G5 in the order named from the first surface A side, in which thefirst lens unit G1 to the fourth lens unit G4 correspond to the frontlens unit GF and in which the fifth lens unit G5 corresponds to the rearlens unit GR.

The first lens unit G1 has a negative lens L11 of the meniscus shapewith a convex surface facing to the first surface A side, and a negativelens L12 of the meniscus shape with a concave surface facing to thefirst surface A side, in the order named from the first surface A side,and these negative lenses L11, L12 form a gas lens of the biconvexshape. The lens surface on the first surface A side of the negative lensL11 and the lens surface on the second surface B side of the negativelens L12 are formed as aspheric surfaces ASP1 and ASP2, respectively.These two negative lenses L11, L12 are made both of silica glass.

The second lens G2 has a positive lens L21 of the meniscus shape with aconcave surface facing to the first surface A side, three positivelenses L22 to L24 of the biconvex shape, and a positive lens L25 of themeniscus shape with a convex surface facing to the first surface A side,in the order named from the first surface A side. The lens surface onthe first surface A side of the positive lens L25 closest to the secondsurface B is formed as an aspheric surface ASP3. All the lenses in thesecond lens unit G2 are made of silica glass.

The third lens unit G3 has a negative lens L31 of the meniscus shapewith a convex surface facing to the first surface A side, and twonegative lenses L32, L33 of the biconcave shape in the order named fromthe first surface A side, and these negative lenses L31 to L33 form twogas lenses of the biconvex shape. Here the lens surface on the secondsurface B side of the negative lens L33 closest to the second surface Bis formed as an aspheric surface ASP4. All the negative lenses L31 toL33 in the third lens unit G3 are made of silica glass.

The fourth lens unit G4 has a positive lens L41 of the meniscus shapewith a concave surface facing to the first surface A side, a positivelens L42 of the meniscus shape with a concave surface facing to thefirst surface A side, and a positive lens L43 of the biconvex shape inthe order named from the first surface A side. Here the two positivelenses L41, L42 are made of silica glass and the positive lens L43 onthe second surface B side is made of fluorite.

The fifth lens unit G5 has a negative lens L51 of the biconcave shape,two positive lenses L52, L53 of the biconvex shape, three positivelenses L54 to L56 of the meniscus shape with a convex surface facing tothe first surface A side, and a negative lens L57 of the biconcave shapein the order named from the first surface A side. Here the lens surfaceon the second surface B side of the negative lens L51 and the lenssurface on the second surface B side of the positive lens L56 are formedas aspheric surfaces ASP5 and ASP6, respectively. In the fifth lens unitG5, only the negative lens L57 closest to the second surface B is madeof fluorite and the other lenses L51 to L56 are made of silica glass.

In the fourth embodiment, as described above, silica glass (syntheticquartz) and fluorite are used as the lens materials (glass materials)and all the lens surfaces of the aspheric shape are formed in the lensesof silica glass.

FIG. 12 is the optical path diagram of the projection optical systemaccording to the fifth embodiment. In this fifth embodiment, silicaglass (synthetic quartz) is used as the principal material (secondmaterial) of the radiation-transmitting refractors in the projectionoptical system and fluorite as the achromatizing material (firstmaterial).

As shown in FIG. 12, the projection optical system of the fifthembodiment has the front lens unit GF of the positive refracting power,the aperture stop AS, and the rear lens unit GR of the positiverefracting power in the order named from the first surface A side.According to another grouping, the projection optical system of thefifth embodiment has the negative, first lens unit G1, the positive,second lens unit G2, the negative, third lens unit G3, the positive,fourth lens unit G4, the aperture stop AS, and the positive, fifth lensunit G5 in the order named from the first surface A side, in which thefirst lens unit G1 to the fourth lens unit G4 correspond to the frontlens unit GF and in which the fifth lens unit G5 corresponds to the rearlens unit GR.

The first lens unit G1 has a negative lens L11 of the planoconcave shapewith a plane facing to the first surface A side, and a negative lens L12of the meniscus shape with a concave surface facing to the first surfaceA side, in the order named from the first surface A side, and thesenegative lenses L11, L12 form a gas lens of the biconvex shape. The lenssurface on the second surface B side of the negative lens L11 is formedas an aspheric surface ASP1. These two negative lenses L11, L12 are madeboth of silica glass.

The second lens G2 has a negative lens L21 of the meniscus shape with aconcave surface facing to the first surface A side, a positive lens L22of the meniscus shape with a concave surface facing to the first surfaceA side, a positive lens L23 of the biconvex shape, and two positivelenses L24, L25 of the meniscus shape with a convex surface facing tothe first surface A side, in the order named from the first surface Aside. The lens surface on the first surface A side of the negative lensL21 closest to the first surface A is formed as an aspheric surfaceASP2. All the lenses in the second lens unit G2 are made of silicaglass.

The third lens unit G3 has a negative lens L31 of the meniscus shapewith a convex surface facing to the first surface A side, and twonegative lenses L32, L33 of the biconcave shape in the order named fromthe first surface A side, and these negative lenses L31 to L33 form twogas lenses of the biconvex shape. Here the lens surface on the secondsurface B side of the negative lens L31 closest to the first surface Aand the lens surface on the second surface B side of the negative lensL33 closest to the second surface B are formed as aspheric surfaces ASP3and ASP4, respectively. All the negative lenses L31 to L33 in the thirdlens unit G3 are made of silica glass.

The fourth lens unit G4 has a positive lens L41 of the meniscus shapewith a concave surface facing to the first surface A side, a positivelens L42 of the meniscus shape with a concave surface facing to thefirst surface A side, and a positive lens L43 of the biconvex shape inthe order named from the first surface A side. Here the two positivelenses L41, L42 on the first surface A side are made of fluorite and thepositive lens L43 on the second surface B side is made of silica glass.

The fifth lens unit G5 has a negative lens L51 of the biconcave shape,two positive lenses L52, L53 of the biconvex shape, three positivelenses L54 to L56 of the meniscus shape with a convex surface facing tothe first surface A side, and a negative lens L57 of the planoconcaveshape with a concave surface facing to the first surface A side, in theorder named from the first surface A side. Here the lens surface on thesecond surface B side of the negative lens L51 and the lens surface onthe second surface B side of the positive lens L55 are formed asaspheric surfaces ASP5 and ASP6, respectively. In the fifth lens unitG5, only the two lenses L56, L57 closest to the second surface B aremade of fluorite and the other lenses L51 to L55 are made of silicaglass.

In the fifth embodiment, as described above, silica glass (syntheticquartz) and fluorite are also used as the lens materials (glassmaterials) and all the lens surfaces of the aspheric shape are formed inthe lenses of silica glass.

FIG. 13 is the optical path diagram of the projection optical systemaccording to the sixth embodiment. In this sixth embodiment, silicaglass (synthetic quartz) is used as the principal material (secondmaterial) of the radiation-transmitting refractors in the projectionoptical system and fluorite as the achromatizing material (firstmaterial).

As shown in FIG. 13, the projection optical system of the sixthembodiment is a double waist type imaging optical system having thefront lens unit GF of the positive refracting power, the aperture stopAS, and the rear lens unit GR of the positive refracting power in theorder named from the first surface A side.

The front lens unit GF has a negative lens L11 of the biconcave shape,three positive lenses L12 to L14 of the biconvex shape, a negative lensL15 of the meniscus shape with a convex surface facing to the firstsurface A side, a positive lens L16 of the biconvex shape, a negativelens L17 of the biconcave shape, two negative lenses L18, L19 of thebiconcave shape, a negative lens L20 of the meniscus shape with aconcave surface facing to the first surface A side, a positive lens L21of the meniscus shape with a concave surface facing to the first surfaceA side, a positive lens L22 of the biconvex shape, a positive lens L23of the meniscus shape with a concave surface facing to the first surfaceA side, two positive lenses L24, L25 of the biconvex shape, a negativelens L26 of the meniscus shape with a convex surface facing to the firstsurface A side, a negative lens L27 of the biconcave shape, a negativelens L28 of the meniscus shape with a concave surface facing to thefirst surface A side, and a positive lens L29 of the meniscus shape witha concave surface facing to the first surface A side, in the order namedfrom the first surface A side. Then the lens surface on the firstsurface A side of the negative lens L20, the lens surface on the firstsurface A side of the negative lens L27, and the lens surface on thesecond surface B side of the negative lens L28 are formed as asphericsurfaces ASP1, ASP2, and ASP3, respectively. Only the positive lens L29closest to the second surface B is made of fluorite and the other lensesL11 to L28 are made all of silica glass.

The rear lens unit GR has two positive lenses L51, L52 of the biconvexshape, a negative lens L53 of the meniscus shape with a concave surfacefacing to the first surface A side, a positive lens L54 of the biconvexshape, three positive lenses L55 to L57 of the meniscus shape with aconvex surface facing to the first surface A side, a negative lens L58of the meniscus shape with a convex surface facing to the first surfaceA side, and a positive lens L59 of the biconvex shape in the order namedfrom the first surface A side. Here the four lenses L53, L54, L58, L59are made as silica lenses and the other five lenses L51, L52, L55, L56,L57 are made of fluorite.

In the sixth embodiment, as described above, silica glass (syntheticquartz) and fluorite are also used as the lens materials (glassmaterials) and all the lens surfaces of the aspheric shape are formed inthe lenses of silica glass.

FIG. 14 is the optical path diagram of the projection optical systemaccording to the seventh embodiment. In this seventh embodiment, silicaglass (synthetic quartz) is used as the principal material (secondmaterial) of the radiation-transmitting refractors in the projectionoptical system and fluorite as the achromatizing material (firstmaterial).

As shown in FIG. 14, the projection optical system of the seventhembodiment is a double waist type imaging optical system having thefront lens unit GF of the positive refracting power, the aperture stopAS, and the rear lens unit GR of the positive refracting power in theorder named from the first surface A side.

The front lens unit GF has a negative lens L11 of the biconcave shape,three positive lenses L12 to L14 of the biconvex shape, a negative lensL15 of the meniscus shape with a convex surface facing to the firstsurface A side, a positive lens L16 of the meniscus shape with a concavesurface facing to the first surface A side, a negative lens L17 of themeniscus shape with a convex surface facing to the first surface A side,two negative lenses L18, L19 of the biconcave shape, a negative lens L20of the meniscus shape with a concave surface facing to the first surfaceA side, a positive lens L21 of the meniscus shape with a concave surfacefacing to the first surface A side, a positive lens L22 of the biconvexshape, a positive lens L23 of the meniscus shape with a concave surfacefacing to the first surface A side, a positive lens L24 of the meniscusshape with a convex surface facing to the first surface A side, apositive lens L25 of the biconvex shape, a negative lens L26 of themeniscus shape with a convex surface facing to the first surface A side,two negative lenses L27, L28 of the biconcave shape, and a positive lensL29 of the meniscus shape with a concave surface facing to the firstsurface A side, in the order named from the first surface A side. Thenthe lens surface on the first surface A side of the negative lens L20,the lens surface on the first surface A side of the negative lens L27,and the lens surface on the second surface B side of the negative lensL28 are formed as aspheric surfaces ASP1, ASP2, and ASP3, respectively.Only the positive lens L29 closest to the second surface B and thepositive lens L24 in the middle are made of fluorite and the otherlenses L11 to L23, L25 to L28 are made all of silica glass.

The rear lens unit GR has two positive lenses L51, L52 of the biconvexshape, a negative lens L53 of the meniscus shape with a concave surfacefacing to the first surface A side, a positive lens L54 of the biconvexshape, three positive lenses L55 to L57 of the meniscus shape with aconvex surface facing to the first surface A side, a negative lens L58of the biconcave shape, and a positive lens L59 of the biconvex shape inthe order named from the first surface A side. Here the four lenses L53,L54, L58, L59 are made as silica lenses and the other five lenses L51,L52, L55, L56, L57 are made of fluorite.

In the seventh embodiment, as described above, silica glass (syntheticquartz) and fluorite are also used as the lens materials (glassmaterials) and all the lens surfaces of the aspheric shape are formed inthe lenses of silica glass.

Next, the lens configuration of the projection optical system accordingto the eighth embodiment of the present example is the same as that ofthe second embodiment of FIG. 2. However, the second embodiment wasdesigned to effect the chromatic aberration correction in the range ofthe wavelength band ±0.4 pm for the reference wavelength of 193.306 nm,whereas this eighth embodiment is arranged to effect the chromaticaberration correction in the range of FWHM (full width at half maximum)of 0.35 pm centered about 193.3 nm, i.e., in the range of 193.3 nm±0.175pm. This range is substantially equivalent to the color correction rangeof the second embodiment (the range of the wavelength band ±0.4 pm forthe reference wavelength).

Table 4 to Table 8 below provide the specifications of the projectionoptical systems of the third embodiment to the seventh embodiment,respectively. In Table 4 to Table 8, the left end column indicatesnumbers of the respective lens surfaces from the first surface A, thesecond column indicates radii of curvature of the respective lenssurfaces, the third column indicates surface spacings from each lenssurface to a next lens surface, the fourth column indicates lensmaterials, the fifth column indicates symbols of the aspheric surfaces,the sixth column indicates the symbols of the respective lenses, and theseventh column indicates clear aperture diameters Φ_(eff) of therespective lens surfaces. A radius of curvature in the second column foreach aspheric lens surface represents a radius of curvature at a vertexthereof. The aspheric shape is expressed by foregoing Eq. (a).

In the last part of Table 4 to Table 8 there are presented the conicalcoefficient κ and the aspheric coefficients A, B, C, D, E, F for eachaspheric surface as [aspheric data].

In the third embodiment to the seventh embodiment, the refractive indexat the reference wavelength (193.3 nm), the change (dispersion) ofrefractive index per wavelength+1 pm, and specific gravity of silicaglass (synthetic quartz) are as follows.

refractive index of silica glass: 1.560326

dispersion of silica glass: −1.591×10⁻⁶/pm

specific gravity of silica glass: 2.2

Further, the refractive index at the above reference wavelength (193.3nm), the change (dispersion) of refractive index per wavelength+1 pm,and the specific gravity of fluorite are as follows.

refractive index of fluorite: 1.501455

dispersion of fluorite: −0.980×10⁻⁶/pm

specific gravity of fluorite: 3.18

In Table 4 to Table 8 below, SiO₂ indicates silica glass, CaF₂ fluorite,d0 the distance from the first surface A to the lens surface closest tothe first surface A, and WD the distance from the lens surface closestto the second surface B, to the second surface B (workpieceingdistance).

Being common to the third embodiment to the seventh embodiment, thenumerical aperture NA of the projection optical system (the maximumnumerical aperture NAw on the second surface B side), the projectionmagnification β, and the diameter φ of the image circle on the secondsurface B are as follows.

NA=0.75

β=−1/4

φ=27.5 mm

TABLE 4 Third Embodiment (FIG. 10) d0 = 55.000001 (mm) WD = 11.000007(mm) Radius of curvature Spacing Aspheric Ø_(eff) (mm) (mm) Glasssurface Lens (mm)  1: 7091.42905 15.000000 Si0₂ ASP1 L11 65.764267  2:355.28402 26.433708 67.469398  3: −130.38826 25.918810 Si0₂ L1267.725563  4: −754.54900 17.524438 ASP2 83.206055  5: −184.7565250.000000 Si0₂ L21 83.795761  6: −201.31203 1.000000 106.116302  7:−19890.02238 49.483069 Si0₂ L22 122.397278  8: −316.51565 1.000000129.413116  9: 1245.95085 42.403865 Si0₂ L23 138.357544 10: −498.4277166.560407 140.000000 11: 278.47126 51.637906 Si0₂ L24 141.615372 12:−5012.84861 1.000000 139.454163 13: 289.66134 44.179422 Si0₂ ASP3 L25129.500671 14: −2001.37857 42.267253 124.865738 15: 790.93523 49.069868Si0₂ L31 91.125748 16: 135.96684 33.309217 65.088898 17: −267.8784017.040059 Si0₂ L32 61.547058 18: 270.92888 19.267729 57.542892 19:−142.62085 16.121708 Si0₂ L33 57.458405 20: 178.57511 16.822454 ASP461.534664 21: −421.32209 50.000000 Si0₂ L41 61.972908 22: −259.465761.000000 76.112648 23: −2487.25765 50.000000 Si0₂ L42 79.889153 24:−308.14629 76.768520 88.439072 25: 280.00000 41.127434 Si0₂ L43108.679848 26: −720.48955 1.000000 108.229263 27: ∞ 42.733304 AS106.832184 28: −291.63339 24.106015 Si0₂ L51 104.909050 29: 462.500543.915270 ASP5 111.616905 30: 471.58425 40.504164 Si0₂ L52 112.104271 31:−415.23032 1.000000 114.105286 32: 454.04392 43.243602 Si0₂ L53118.187286 33: −454.04392 16.312093 117.964470 34: 165.07875 34.495142Si0₂ L54 104.927750 35: 339.14804 1.000000 100.211807 36: 150.0000050.000000 Si0₂ L55 92.390938 37: 224.50669 1.706390 75.144737 38:129.56425 36.373254 Si0₂ L56 69.153374 39: 270.95319 6.298515 ASP654.786152 40: −21804.34155 50.000000 Si0₂ L57 53.646206 41: ∞ (WD)26.202827 [Aspheric Data] ASP1 κ: 0.000000 A: 0.961814 × 10⁻⁷ B:−0.378122 × 10⁻¹¹ C: 0.392716 × 10⁻¹⁶ D: 0.424498 × 10⁻²⁰ E: −0.220614 ×10⁻²³ F: 0.200305 × 10⁻²⁷ ASP2 κ: 0.000000 A: 0.263695 × 10⁻⁷ B:−0.882693 × 10⁻¹² C: 0.290428 × 10⁻¹⁶ D: 0.285450 × 10⁻²¹ E: −0.170241 ×10⁻²⁴ F: 0.929230 × 10⁻²⁹ ASP3 κ: 0.000000 A: −0.889053 × 10⁻⁸ B:−0.224185 × 10⁻¹² C: −0.211101 × 10⁻¹⁷ D: −0.108571 × 10⁻²² E: 0.470441× 10⁻²⁷ F: 0.130782 × 10⁻³¹ ASP4 κ: 0.000000 A: 0.408033 × 10⁻⁷ B:−0.582850 × 10⁻¹¹ C: 0.132297 × 10⁻¹⁵ D: 0.117896 × 10⁻¹⁹ E: −0.974397 ×10⁻²⁴ F: 0.578268 × 10⁻²⁸ ASP5 κ: 0.000000 A: 0.186307 × 10⁻⁷ B:−0.146992 × 10⁻¹³ C: −0.448096 × 10⁻¹⁷ D: −0.180733 × 10⁻²² E: 0.986636× 10⁻²⁷ F: −0.118893 × 10⁻³¹ ASP6 κ: 0.000000 A: −0.256013 × 10⁻⁷ B:−0.517336 × 10⁻¹¹ C: 0.740082 × 10⁻¹⁶ D: −0.106082 × 10⁻¹⁹ E: 0.506294 ×10⁻²³ F: −0.312361 × 10⁻²⁷

TABLE 5 Fourth Embodiment (FIG. 11) d0 = 61.517734 (mm) WD = 11.723518(mm) Radius of curvature Spacing Aspheric Ø_(eff) (mm) (mm) Glasssurface Lens (mm)  1: 850.22148 15.762264 Si0₂ ASP1 L11 67.516739  2:258.78675 32.754986 68.621666  3: −120.04708 29.316457 Si0₂ L1269.040245  4: −1436.64708 14.154830 ASP2 88.608788  5: −262.9341349.861514 Si0₂ L21 89.277542  6: −204.39549 1.000000 108.090843  7:4807.74825 47.706981 Si0₂ L22 124.939384  8: −334.63584 1.000000130.588333  9: 943.02750 38.323507 Si0₂ L23 138.787674 10: −755.2004252.297712 139.999893 11: 314.45430 52.295370 Si0₂ L24 142.105682 12:−1342.07699 1.000000 140.302780 13: 220.89539 44.997489 Si0₂ ASP3 L25125.209908 14: 1112.83084 35.915976 119.146675 15: 578.45483 47.943238Si0₂ L31 94.646919 16: 137.07988 34.945536 68.147148 17: −290.2403022.821650 Si0₂ L32 64.390198 18: 284.15051 19.770859 59.085491 19:−144.74289 15.000000 Si0₂ L33 58.975883 20: 182.17660 18.923653 ASP462.526440 21: −316.81092 50.000000 Si0₂ L41 62.945671 22: −235.352051.000000 77.530685 23: −1288.79277 48.502244 Si0₂ L42 81.365692 24:−310.15694 87.817988 90.067673 25: 280.00000 44.217287 CaF₂ L43114.022461 26: −726.81420 1.000000 113.702507 27: ∞ 34.906154 AS112.151863 28: −321.35755 24.106015 Si0₂ L51 111.345039 29: 527.144503.208930 ASP5 117.654945 30: 526.07539 41.883852 Si0₂ L52 117.834465 31:−420.10068 1.000000 119.874275 32: 501.17942 44.518152 Si0₂ L53124.057274 33: −518.35529 23.847453 123.851112 34: 187.05620 37.766684Si0₂ L54 111.266914 35: 401.71759 3.209637 105.841919 36: 150.1873850.000000 Si0₂ L55 96.210228 37: 247.90367 7.654279 80.668587 38:129.88090 35.932549 Si0₂ L56 70.574219 39: 296.77641 6.269996 ASP657.089531 40: −55171.62371 50.000000 CaF₂ L57 55.946609 41: 8863.22783(WD) 26.976627 [Aspheric Data] ASP1 κ: 0.000000 A: 0.973900 × 10⁻⁷ B:−0.304719 × 10⁻¹¹ C: 0.103626 × 10⁻¹⁵ D: 0.933452 × 10⁻²⁰ E: −0.259784 ×10⁻²³ F: 0.281860 × 10⁻²⁷ ASP2 κ: 0.000000 A: 0.525544 × 10⁻⁸ B:−0.471274 × 10⁻¹² C: 0.546888 × 10⁻¹⁶ D: −0.177219 × 10⁻²⁰ E: 0.249175 ×10⁻²⁶ F: 0.442229 × 10⁻²⁹ ASP3 κ: 0.000000 A: −0.378457 × 10⁻⁸ B:−0.141446 × 10⁻¹² C: −0.231375 × 10⁻¹⁷ D: −0.721926 × 10⁻²² E: −0.407320× 10⁻²⁷ F: −0.595894 × 10⁻³¹ ASP4 κ: 0.000000 A: 0.607276 × 10⁻⁷ B:−0.700544 × 10⁻¹¹ C: 0.760900 × 10⁻¹⁶ D: 0.201180 × 10⁻¹⁹ E: −0.160443 ×10⁻²³ F: 0.856074 × 10⁻²⁸ ASP5 κ: 0.000000 A: 0.157329 × 10⁻⁷ B:−0.167548 × 10⁻¹⁴ C: −0.304998 × 10⁻¹⁷ D: −0.499814 × 10⁻²³ E: 0.552478× 10⁻²⁷ F: −0.684401 × 10⁻³² ASP6 κ: 0.000000 A: −0.183007 × 10⁻⁷ B:−0.320743 × 10⁻¹¹ C: 0.474775 × 10⁻¹⁶ D: −0.990352 × 10⁻²⁰ E: 0.269071 ×10⁻²³ F: −0.170233 × 10⁻²⁷

TABLE 6 Fifth Embodiment (FIG. 12) d0 = 55.000003 (mm) WD = 10.999994(mm) Radius of Aspher- curvature Spacing ic Ø_(eff) (mm) (mm) Glasssurface Lens (mm)  1: ∞ 15.000000 Si0₂ L11 65.321190  2: 314.6270427.244624 ASP1 67.796265  3: −123.18686 27.378474 Si0₂ L12 68.086769  4:−266.68374 14.602794 82.068336  5: −150.00000 50.000000 Si0₂ ASP2 L2182.538231  6: −244.34192 1.000000 110.219063  7: −1198.84474 44.914055Si0₂ L22 122.357353  8: −232.66356 1.000000 127.431076  9: 5275.6425243.090859 Si0₂ L23 137.635925 10: −360.63034 5.030036 139.581192 11:285.72583 47.577067 Si0₂ L24 139.546677 12: 4561.05389 6.030041136.970505 13: 212.35017 50.000000 Si0₂ L25 124.093590 14: 796.0329635.691263 116.083298 15: 762.23216 50.000000 Si0₂ L31 95.138901 16:147.63565 50.187741 ASP3 69.070221 17: −185.70008 15.000000 Si0₂ L3261.216537 18: 639.43295 15.701720 59.080795 19: −153.51758 15.000000Si0₂ L33 59.002586 20: 185.58159 20.611177 ASP4 63.036831 21: −255.8771650.000000 CaF₂ L41 63.577843 22: −249.68527 3.980529 80.211006 23:−3778.76287 35.000000 CaF₂ L42 86.501961 24: −224.75345 129.59955790.822037 25: 280.00000 50.000000 Si0₂ L43 120.569611 26: −913.1288610.916703 119.561447 27: ∞ 33.865871 AS 117.247459 28: −361.6262224.106015 Si0₂ L51 115.516739 29: 416.11728 5.557131 ASP5 118.568176 30:416.69495 44.381334 Si0₂ L52 119.549057 31: −543.90687 1.000000120.733887 32: 590.20673 38.166548 Si0₂ L53 121.085487 33: −590.2067324.232291 120.207893 34: 180.00000 39.243850 Si0₂ L54 108.463890 35:309.38340 8.819688 101.371346 36: 150.00000 50.000000 Si0₂ L55 92.78100637: 225.00345 1.166306 ASP6 77.138145 38: 114.38119 43.612328 CaF₂ L5670.172379 39: 390.97069 5.290357 54.909901 40: −7097.28080 50.000000CaF₂ L57 53.587784 41: ∞ (WD) 25.551462 [Aspheric Data] ASP1 κ: 0.000000A: −0.969228 × 10⁻⁷ B: 0.326972 × 10⁻¹¹ C: −0.944059 × 10⁻¹⁶ D: 0.473154× 10⁻²⁰ E: 0.728259 × 10⁻²⁴ F: −0.582964 × 10⁻²⁹ ASP2 κ: 0.000000 A:−0.243951 × 10⁻⁷ B: −0.120134 × 10⁻¹¹ C: −0.659871 × 10⁻¹⁶ D: −0.399458× 10⁻²⁰ E: −0.878285 × 10⁻²⁵ F: −0.231429 × 10⁻²⁸ ASP3 κ: 0.000000 A:0.293300 × 10⁻⁸ B: 0.197746 × 10⁻¹¹ C: 0.885710 × 10⁻¹⁶ D: 0.335600 ×10⁻²⁰ E: 0.761535 × 10⁻²⁴ F: 0.365525 × 10⁻²⁸ ASP4 κ: 0.000000 A:0.506090 × 10⁻⁷ B: −0.926440 × 10⁻¹¹ C: 0.292340 × 10⁻¹⁵ D: 0.202698 ×10⁻¹⁹ E: −0.264577 × 10⁻²³ F: 0.125177 × 10⁻²⁷ ASP5 κ: 0.000000 A:0.142370 × 10⁻⁷ B: 0.564687 × 10⁻¹³ C: −0.238454 × 10⁻¹⁷ D: −0.231787 ×10⁻²² E: 0.248738 × 10⁻²⁷ F: −0.396109 × 10⁻³² ASP6 κ: 0.000000 A:0.328323 × 10⁻⁸ B: −0.104463 × 10⁻¹¹ C: −0.354474 × 10⁻¹⁶ D: −0.125502 ×10⁻²⁰ E: −0.370501 × 10⁻²⁷ F: 0.157184 × 10⁻²⁹

TABLE 7 Sixth Embodiment (FIG. 13) d0 = 63.749760 (mm) WD = 11.204291(mm) Radius of curvature Spacing Aspheric Ø_(eff) (mm) (mm) Glasssurface Lens (mm)  1: −384.26106 15.000000 Si0₂ L11 65.998985  2:281.85126 11.978853 71.535873  3: 348.95782 28.971808 Si0₂ L12 77.330864 4: −344.97594 1.000000 79.541092  5: 838.59364 22.091944 Si0₂ L1382.133408  6: −491.36531 1.000000 82.994720  7: 404.67369 24.295064 Si0₂L14 83.439461  8: −747.56330 1.000000 82.796455  9: 231.07842 15.000000Si0₂ L15 79.702614 10: 134.40371 10.555015 74.346352 11: 220.9819431.018759 Si0₂ L16 74.341751 12: −376.01279 1.000000 72.918823 13:−2565.43982 31.296610 Si0₂ L17 70.508438 14: 150.78493 21.34269561.532974 15: −265.42164 15.000000 Si0₂ L18 61.468307 16: 205.7468622.633359 62.887703 17: −175.10057 15.000000 Si0₂ L19 63.156342 18:384.28896 26.307128 73.675224 19: −337.20967 15.000000 Si0₂ ASP1 L2081.524727 20: −2665.09055 11.890080 92.491890 21: −355.33094 23.660088Si0₂ L21 93.401833 22: −212.64088 1.000000 100.326263 23: 9025.0329837.428886 Si0₂ L22 118.812363 24: −307.87323 1.000000 123.020493 25:−3478.34934 35.232416 Si0₂ L23 131.558868 26: −350.00000 1.000000134.129471 27: 655.38208 45.610359 Si0₂ L24 139.999451 28: −513.319741.000000 140.078323 29: 213.32620 57.138993 Si0₂ L25 130.179550 30:−4397.04839 33.096623 126.273247 31: 887.72778 15.000000 Si0₂ L26100.220100 32: 161.65056 57.435235 85.838745 33: −157.17781 15.000000Si0₂ ASP2 L27 82.709534 34: 219.87361 32.150950 84.204674 35: −255.3912015.000000 Si0₂ L28 84.510979 36: −8581.78601 11.405070 ASP3 93.47895137: −388.87067 44.944016 CaF₂ L29 94.167152 38: −218.37501 1.000000106.093346 39: ∞ 14.244161 AS 113.779617 40: 2733.87010 44.018422 CaF₂L51 121.696854 41: −283.88458 1.000000 124.288734 42: 336.3052543.993297 CaF₂ L52 133.359390 43: −1641.02052 26.208757 133.284454 44:−305.07796 25.000000 Si0₂ L53 133.233185 45: −428.53617 9.225281137.790878 46: 704.67535 38.550758 Si0₂ L54 139.115891 47: −708.094921.000000 138.525772 48: 210.28367 39.284351 CaF₂ L55 126.898781 49:533.77492 1.000000 122.815582 50: 178.50760 37.746739 CaF₂ L56111.402145 51: 379.62268 1.057673 104.079216 52: 169.01250 33.580626CaF₂ L57 93.513443 53: 510.82832 7.325751 84.815453 54: 4574.6496350.000000 Si0₂ L58 83.638657 55: 379.11421 2.326181 53.309875 56:563.01655 50.000000 Si0₂ L59 52.367188 57: −4692.22208 (WD) 26.519352[Aspheric Data] ASP1 κ: 0.000000 A: 0.216518 × 10⁻⁷ B: 0.109348 × 10⁻¹¹C: 0.396907 × 10⁻¹⁶ D: 0.177070 × 10⁻²⁰ E: 0.301350 × 10⁻²⁵ F: 0.748178× 10⁻²⁹ ASP2 κ: 0.339337 A: 0.468446 × 10⁻⁸ B: 0.323507 × 10⁻¹¹ C:−0.277057 × 10⁻¹⁷ D: 0.454850 × 10⁻²⁰ E: −0.183005 × 10⁻²⁴ F: 0.121371 ×10⁻²⁸ ASP3 κ: 0.000000 A: −0.170958 × 10⁻⁷ B: 0.631731 × 10⁻¹² C:−0.315858 × 10⁻¹⁶ D: 0.957027 × 10⁻²¹ E: −0.298216 × 10⁻²⁵ F: −0.655478× 10⁻³⁰

TABLE 8 Seventh Embodiment (FIG. 14) d0 = 63.749746 (mm) WD = 13.389654(mm) Radius of curvature Spacing Aspheric Ø_(eff) (mm) (mm) Glasssurface Lens (mm)  1: −396.81755 15.164101 Si0₂ L11 66.032784  2:318.45576 29.207879 71.297302  3: 732.28117 25.666287 Si0₂ L12 83.471970 4: −379.10485 1.000000 86.041710  5: 525.04598 29.799021 Si0₂ L1390.425125  6: −386.12241 1.000000 91.317108  7: 296.71481 27.521447 Si0₂L14 91.079468  8: −1834.92841 1.000000 89.757446  9: 178.21689 15.000000Si0₂ L15 84.396111 10: 128.82838 30.507210 77.857750 11: −912.3430518.141324 Si0₂ L16 77.741890 12: −290.65675 1.000000 77.271347 13:2184.51382 47.405470 Si0₂ L17 74.290833 14: 188.39849 24.66716865.022842 15: −180.63293 15.000000 Si0₂ L18 64.974625 16: 308.3208719.189943 68.677689 17: −233.12081 15.000000 Si0₂ L19 68.994057 18:439.39083 32.120556 79.245667 19: −336.14512 15.000000 Si0₂ ASP1 L2089.338654 20: −2278.87871 10.459773 101.857063 21: −456.23451 24.690274Si0₂ L21 102.820465 22: −254.53495 1.000000 110.024078 23: 2814.3479554.862219 Si0₂ L22 131.136322 24: −244.85996 1.000000 135.344131 25:−1839.77632 33.926267 Si0₂ L23 144.103409 26: −387.77935 1.000000146.107864 27: 350.00000 44.271958 CaF₂ L24 149.999664 28: 22107.528321.000000 148.725906 29: 254.93631 55.237937 Si0₂ L25 141.298035 30:−6319.95498 31.357005 137.595520 31: 664.06027 18.849345 Si0₂ L26112.356766 32: 185.98655 69.207456 96.853653 33: −174.34160 15.000000Si0₂ ASP2 L27 91.180862 34: 227.17956 38.807665 92.023659 35: −241.6210015.000000 Si0₂ L28 92.325920 36: 4079.61757 15.799849 ASP3 103.72185537: −376.03072 39.964600 CaF₂ L29 104.289635 38: −218.60371 1.000000114.670761 39: ∞ 6.289754 AS 125.662186 40: 1034.55937 49.970241 CaF₂L51 133.965057 41: −321.64602 1.000000 136.199570 42: 468.8493148.186456 CaF₂ L52 143.242279 43: −704.77302 17.319103 143.524338 44:−346.54415 25.000000 Si0₂ L53 143.458008 45: −611.18135 5.972669147.975433 46: 506.91799 50.000000 Si0₂ L54 150.196625 47: −1493.042886.590003 148.599213 48: 277.37401 50.000000 CaF₂ L55 139.059814 49:1289.11360 7.965482 133.022858 50: 179.54228 44.409645 CaF₂ L56114.913353 51: 446.48076 1.057673 106.338089 52: 182.12642 32.279024CaF₂ L57 95.185760 53: 558.39361 8.108756 86.695763 54: −10831.2150550.000000 Si0₂ L58 85.506866 55: 322.39407 2.037539 54.834679 56:399.72415 50.000000 Si0₂ L59 53.968300 57: −1901.87993 (WD) 29.165956[Aspheric Data] ASP1 κ: 0.000000 A: 0.894266 × 10⁻⁸ B: 0.474065 × 10⁻¹²C: 0.152423 × 10⁻¹⁶ D: 0.302088 × 10⁻²¹ E: 0.257776 × 10⁻²⁵ F: −0.100658× 10⁻³⁰ ASP2 κ: 0.316202 A: 0.472957 × 10⁻⁸ B: 0.240757 × 10⁻¹¹ C:−0.215896 × 10⁻¹⁶ D: 0.217268 × 10⁻²⁰ E: −0.736783 × 10⁻²⁵ F: 0.336149 ×10⁻²⁹ ASP3 κ: 0.000000 A: −0.155031 × 10⁻⁷ B: 0.622128 × 10⁻¹² C:−0.259658 × 10⁻¹⁶ D: 0.943107 × 10⁻²¹ E: −0.288354 × 10⁻²⁵ F: 0.360267 ×10⁻³⁰

Now Table 9 below presents numerical values corresponding to theconditions in the third embodiment to the seventh embodiment, and in theeighth embodiment (equivalent to the second embodiment). In Table 9, f2indicates the focal length of the rear lens unit GR, NA indicates thenumerical aperture on the second surface B side of the projectionoptical system (=the image-side maximum numerical aperture NAw), φindicates the diameter (mm) of the image circle, β indicates theprojection magnification, y indicates the reduced use amount (kg) offluorite as a disk member, yP indicates the use amount (kg) of fluoriteas the lenses themselves (shape material), and A indicates the number ofaspheric surfaces.

TABLE 9 f2 NA Ø y yP (mm) (NAw) (mm) | β | (kg) (kg) A Embodiment 3128.0 0.75 27.5 0.25 0.0 0.0 6 Embodiment 4 134.2 0.75 27.5 0.25 8.6 5.86 Embodiment 5 140.2 0.75 27.5 0.25 13.5 10.3 6 Embodiment 6 141.6 0.7527.5 0.25 45.2 24.7 3 Embodiment 7 156.4 0.75 27.5 0.25 65.9 37.3 3Embodiment 8 128.3 0.75 26.6 0.25 14.1 7.9 6

Next, Table 10 provides the fluorite amount y in FIG. 8 and FIG. 9, andthe results of calculation of the parameter x (=f2 . 4|β|. NAw²) foreach of the embodiments, based on above Table 9. Table 10 furtherpresents values of f2/NAw, which are calculated by dividing the focallength f2 of the rear lens unit GR by the image-side maximum numericalaperture NAw (=NA) of the projection optical system, for each of theembodiments.

TABLE 10 y (amount X (= f2 · 4 | β | · NAw²) of fluorite) f2/NAw (mm)(kg) (mm) Embodiment 3 72.000 0.0 170.67 Embodiment 4 75.488 8.6 178.93Embodiment 5 78.863 13.5 186.93 Embodiment 6 79.650 45.2 188.80Embodiment 7 87.975 65.9 208.53 Embodiment 8 72.169 14.1 171.07

The data A3 to A8 (A2) of (x, y) in the third embodiment to the eighthembodiment (the second embodiment), obtained from Table 10, are plottedin FIG. 8 and FIG. 9. These data A3 to A8 are all in the range of theregion B5 and the region C5, and thus these embodiments satisfy theconditions (11) to (14) and the conditions (15) to (18). Further, theseembodiments all satisfy the conditions (d-1), (d-2). The thirdembodiment to the sixth embodiment, and the eighth embodiment (thesecond embodiment) satisfy the condition (e).

The third embodiment to the fifth embodiment, and the eighth embodiment(the second embodiment) satisfy the conditions (19), (20), and the sixthembodiment and the seventh embodiment satisfy the conditions (21), (22).

Next, Table 11 presents the values corresponding to the conditions ofthe above embodiments concerning the conditions (b-1), (b-2) and (c-1),(c-2) of the aspheric shape. In Table 11, the lens number indicates anumber of the lens having the first aspheric surface when counted fromthe first surface side, in the projection optical system of eachembodiment, and the surface number of aspheric surface a number of theaspheric surface from the first surface. The principal curvature Ca is alocal, principal curvature near the center of the optical axis of theaspheric surface and is calculated according to Eq (b-4). The principalcurvature Cb is a local, principal curvature in the meridional directionof the extreme marginal region of the clear aperture diameter of lensand is calculated according to Eq (b-5).

TABLE 11 Embodiment 3 Embodiment 4 Embodiment 5 Embodiment 8 Lens number1 1 1 1 Surface number 1 1 2 2 of aspheric surface + or − of + + − −refracting power Clear 65.8 67.5 67.8 66.6 aperture diameter (mm)Principal −0.00014 −0.00118 −0.00318 0.00329 curvature Ca Principal−0.00308 −0.00507 0.00000 −0.00234 curvature Cb Cb/Ca 21.860 4.309 0.000−0.711

It is seen from this Table 11 that the third embodiment to the fifthembodiment, and the eighth embodiment (the second embodiment) satisfythe conditions (b-1), (b-2), and (c-1), (c-2) concerning the asphericshape.

In the next place, FIG. 15 to FIG. 20 show the lateral aberration chartson the second surface B of the projection optical systems according tothe third embodiment to the eighth embodiment (the second embodiment),respectively.

Here FIG. 15(A) to FIG. 19(A) are the lateral aberration charts in themeridional direction at the image height Y=13.75, FIG. 15(B) to FIG.19(B) the lateral aberration diagrams in the meridional direction at theimage height Y=6.875, FIG. 15(C) to FIG. 19(C) the lateral aberrationdiagrams in the meridional direction at the image height Y=0 (on theoptical axis), FIG. 15(D) to FIG. 19(D) the lateral aberration diagramsin the sagittal direction at the image height Y=13.75, FIG. 15(E) toFIG. 19(E) the lateral aberration diagrams in the sagittal direction atthe image height Y=6.875, and FIG. 15(F) to FIG. 19(F) the lateralaberration diagrams in the sagittal direction at the image height Y=0(on the optical axis).

FIG. 20(A) is the lateral aberration chart in the meridional directionat the image height Y=13.3, FIG. 20(B) the lateral aberration diagram inthe meridional direction at the image height Y=6.65, FIG. 20(C) thelateral aberration diagram in the meridional direction at the imageheight Y=0 (on the optical axis), FIG. 20(D) the lateral aberrationchart in the sagittal direction at the image height Y=13.3, FIG. 20(E)the lateral aberration diagram in the sagittal direction at the imageheight Y=6.65, and FIG. 20(F) the lateral aberration diagram in thesagittal direction at the image height Y=0 (on the optical axis)

In each of the lateral aberration charts of FIG. 15 to FIG. 20, a solidline represents an aberration curve at the wavelength λ=193.3 nm (thereference wavelength), a dashed line an aberration curve at thewavelength λ=193.3 nm+0.175 pm (the reference wavelength+0.175 pm), anda chain line an aberration curve at the wavelength λ=193.3 nm−0.175 pm(the reference wavelength−0.175 pm).

As apparent from FIG. 15 to FIG. 20, in the projection optical system ofeach embodiment, the chromatic aberration is corrected well across thewavelength region of ±0.175 pm.

Each of the projection optical systems of the third embodiment to theseventh embodiment has the circular image field having the diameter of27.5 mm and can ensure the rectangular exposure area, for example,having the width of about 8 mm in the scanning direction and the widthof about 26 mm in the direction perpendicular to the scanning direction,in the image field. When the projection optical systems of theseembodiments are applied to those of the scanning exposure typeprojection exposure apparatus of the step-and-scan method, thestitch-and-scan method, and so on, high throughput can be yieldedaccordingly.

In the foregoing examples, the rectangular exposure area was employed inconsideration of application of the projection optical system PL of eachembodiment to the scanning exposure apparatus, but the shape of theexposure area can be any area included in the circular image field;e.g., either of various shapes including the hexagonal shape, isoscelestrapezoid, scalene trapezoid, rhomboid, square, arc, and so on.

The foregoing projection optical systems PL of the first embodiment tothe seventh embodiment can be applied to the projection exposureapparatus of the embodiment shown in FIG. 5. FIG. 5 describes an exampleusing the F₂ laser source as a light source and using the firstembodiment as the projection optical system PL, but, for application ofthe projection optical systems PL of the second to seventh embodimentsoptimized for the ArF excimer laser, the fundamental structure ofexposure apparatus except for the light source is also substantially thesame as that in FIG. 5.

The embodiment of the exposure apparatus according to the presentinvention will be described with reference to FIG. 5.

FIG. 5 is a drawing to show the schematic structure of the projectionexposure apparatus according to the embodiment. In FIG. 5 an XYZcoordinate system is adopted.

The exposure apparatus according to the embodiment results fromapplication of the present invention to the projection exposureapparatus using the F₂ laser source as an exposure light source and therefracting optical system as the projection optical system. Theprojection exposure apparatus of the present embodiment employs thestep-and-scan method of sequentially transferring a pattern image of areticle into one shot area on a substrate by synchronous scanning of thereticle and the substrate in a predetermined direction relative to anillumination area of a predetermined shape on the reticle. Such exposureapparatus of the step-and-scan type can transfer the pattern of thereticle into the wider area on the substrate than the exposure field ofthe projection optical system.

In FIG. 5, the laser light source 2 has a combination of a fluorinedimer laser (F₂ laser) having the oscillation frequency of 157 nm with aband narrowing device, for example. The F₂ laser has FWHM of about 1.5pm in spontaneous emission and this F₂ laser is combined with the bandnarrowing device to obtain laser light with FWHM of about 0.2 pm to 0.25pm.

The laser light source 2 in the present embodiment can be one of lightsources emitting light in the vacuum ultraviolet region of thewavelengths of about 120 nm to about 180 nm; e.g., the krypton dimerlaser (Kr₂ laser) having the oscillation wavelength of 146 nm, the argondimer laser (Ar₂ laser) having the oscillation wavelength of 126 nm, andso on.

The pulse laser light (illumination light) from the laser light source 2is deflected by a deflection mirror 3 toward a light delaying opticalsystem 41 to be temporally divided into a plurality of beams with anoptical path difference of not less than the temporal coherence lengthof the illumination light from the laser light source 2. The lightdelaying optical system of this type is disclosed, for example, inJapanese Patent Applications Laid-Open No. H01-198759 and Laid-Open No.H11-174365.

The illumination light emitted from the light delaying optical system 41is deflected by a path deflection mirror 42 and thereafter travelssuccessively through a first fly's eye lens 43, a zoom lens 44, and avibrating mirror 45 to reach a second fly's eye lens 46. A switchingrevolver 5 for an aperture stop of an illumination optical system, whichis for setting the effective size and shape of light source to desiredones, is located on the exit side of the second fly's eye lens 46. Inthe present example, the size of the beam into the second fly's eye lens46 is variable by the zoom lens 44, in order to reduce loss in quantityof light at the aperture stop of the illumination optical system.

The beam emerging from the aperture of the aperture stop of theillumination optical system travels through a condenser lens unit 10 toilluminate an illumination field stop (reticle blind) 11. Theillumination field stop 11 is disclosed in Japanese Patent ApplicationLaid-Open No. H04-196513 and U.S. Pat. No. 5,473,410 correspondingthereto.

The light from the illumination field stop 11 is guided via anillumination-field-stop imaging optical system (reticle-blind imagingsystem) consisting of deflection mirrors 151, 154 and lenses 152, 153,155 onto a reticle R, whereupon an illumination area, which is an imageof the opening portion of the illumination field stop 10, is formed onthe reticle R. The light from the illumination area on the reticle R isguided through the projection optical system PL onto a wafer W,whereupon a reduced image of a pattern in the illumination area of thereticle R is formed on the wafer W.

When the exposure light is light of the wavelength in the vacuumultraviolet region, it is necessary to purge gases having the strongabsorption property for such light in the wavelength band (which will becalled hereinafter “absorptive gases” at need), such as oxygen, watervapor, hydrocarbon-based gases, and so on, from the optical paths.

In the present embodiment, therefore, the illumination optical path (theoptical path from the laser light source 2 to the reticle R) and theprojection optical path (the optical path from the reticle R to thewafer W) are shut off from the external atmosphere and those opticalpaths are filled with a gas of nitrogen, helium, argon, neon, krypton,or the like as a specific gas having the property of little absorbingthe light in the vacuum ultraviolet region, or a mixed gas of two ormore selected therefrom (which will be called hereinafter“low-absorptive gas” or “specific gas” at need).

Specifically, the optical path from the laser source 2 to the lightdelaying optical system 41 is shut off from the external atmosphere bycasing 30, the optical path from the light delaying optical system 41 tothe illumination field stop 11 off from the external atmosphere bycasing 40, the illumination-field-stop imaging optical system off fromthe external atmosphere by casing 150, and the foregoing specific gas isfilled in those optical paths. The projection optical system PL itselfhas a barrel acting as a casing and the internal optical path thereof isfilled with the foregoing specific gas.

The specific gas filled in each optical path is preferably helium.However, nitrogen can also be used as the specific gas in the opticalpaths of the illumination optical system from the laser source 2 to thereticle R (the casings 30, 40, 150).

A casing 170 shuts off the space between the casing 150 housing theillumination-field-stop imaging optical system, and the projectionoptical system PL from the external atmosphere and houses a reticlestage RS for holding the reticle R inside. This casing 170 is providedwith a gate 173 for loading and unloading of the reticle R and a gasreplacement chamber 174 for preventing the atmosphere in the casing 170from being contaminated during loading and unloading of the reticle R,is provided outside the gate 173. This gas replacement chamber 174 isalso provided with a gate 177 and transfer of a reticle is implementedthrough the gate 177 to or from a reticle stocker 210 storing pluraltypes of reticles.

A casing 200 shuts off the space between the projection optical systemPL and the wafer W from the external atmosphere and houses inside, awafer stage 22 for holding the wafer W, an autofocus sensor 26 of anoblique incidence type for detecting the position in the Z-direction(focus position) and inclination angle of the surface of the wafer W asa substrate, an alignment sensor 28 of the off-axis method, and asurface plate 23 carrying the wafer stage 22. This casing 200 isprovided with a gate 203 for loading and unloading of the wafer W, and agas replacement chamber 204 for preventing the atmosphere inside thecasing 200 from being contaminated, is provided outside this gate 203.This gas replacement chamber 204 is equipped with a gate 207 and a waferW is carried into or of the apparatus through this gate 207.

Here each of the casings 40, 150, 170, 200 is provided with an inletvalve 147, 156, 171, or 201, respectively, and these inlet valves 147,156, 171, 201 are connected to an inlet pipe path connected to anunrepresented gas supply. Each of the casings 40, 150, 170, 200 is alsoprovided with an exhaust valve 148, 157, 172, or 202 and these exhaustvalves 148, 157, 172, 202 are connected through an unrepresented exhaustpipe path to the foregoing gas supply. The specific gas from the gassupply is controlled to a predetermined target temperature byunrepresented temperature regulators. When helium is used as thespecific gas, the temperature regulators are preferably located in thevicinity of the respective casings.

Similarly, the gas replacement chambers 174, 204 are also provided withan inlet valve 175 or 205 and an exhaust valve 176 or 206, and the inletvalves 175, 205 are connected through an inlet pipe path while theexhaust valves 176, 206 through an exhaust pipe path, to the foregoinggas supply. Further, the barrel of the projection optical system PL isalso provided with an inlet valve 181 and an exhaust valve 182, and theinlet valve 181 is connected through an unrepresented inlet pipe pathwhile the exhaust valve 182 through an unrepresented exhaust pipe path,to the foregoing gas supply.

The inlet pipe paths connected to the inlet valves 147, 156, 171, 175,181, 201, 205 and the exhaust pipe paths connected to the exhaust valves148, 157, 172, 176, 182, 202, 206 are equipped with a filter forremoving dust (particles), such as a HEPA filter or an ULPA filter, anda chemical filter for removing the absorptive gases including oxygen andthe like.

The gas replacement chambers 174, 204 require gas replacement everyreticle exchange or wafer exchange. For example, on the occasion ofreticle exchange, the gate 174 is opened to permit a reticle to becarried from the reticle stocker 210 into the gas replacement chamber174, the gate 174 is then closed to fill the interior of the gasreplacement chamber 174 with the specific gas, and thereafter the gate173 is opened to mount the reticle onto the reticle stage RS. Duringwafer exchange, the gate 207 is opened to permit a wafer to be carriedinto the gas replacement chamber 204, and then the gate 207 is closed tofill the interior of the gas replacement chamber 204 with the specificgas. After that, the gate 203 is opened to mount the wafer onto thewafer holder 20. Procedures for reticle unloading and wafer unloadingare reverse to the above procedures. The procedures for gas replacementin the gas replacement chamber 174, 204 can be also arranged to firstdecompress the atmosphere in the gas replacement chamber and thereaftersupply the specific gas through the inlet valve.

In the casings 170, 200, there is the possibility of mixing of the gasthereinto on the occasion of the gas replacement in the gas replacementchambers 174, 204 and the gas in the gas replacement chambers 174, 204can contain a considerable amount of the absorptive gases such as oxygenand the like with a high probability. It is thus desirable to carry outgas replacement there at the same timing as the gas replacement in thegas replacement chambers 174, 204. The casings and the gas replacementchambers are preferably filled with the specific gas at a higherpressure than the pressure of the external atmosphere.

In the present embodiment, though not shown in FIG. 5, at least one lenselement of the plurality of lens elements constituting the projectionoptical system PL is held so as to be able to be changed in at least oneof its position and posture. This makes the imaging characteristics ofthe projection optical system PL variable. Such adjusting means aredisclosed, for example, in Japanese Patent Applications Laid-Open No.H04-192317, Laid-Open No. H04-127514 (and U.S. Pat. No. 5,117,255corresponding thereto), Laid-Open No. H05-41344, and Laid-Open No.H06-84527 (and U.S. Pat. No. 5,424,552 corresponding thereto).

In the present embodiment, at least one of the lens elements changeablein at least one of the position and posture is preferably a sphericallens.

The projection optical systems PL of the second to seventh embodimentsoptimized for the ArF excimer laser can be applied to the projectionexposure apparatus disclosed in Japanese Patent Applications Laid-OpenNo. H06-260386 (U.S. Pat. No. 5,559,584), Laid-Open No. H11-233447,WO98/57213, WO99/10917, and WO99/50892, and so on.

The projection exposure apparatus of the present invention is preferablyprovided with the light source for supplying the exposure light in thewavelength region of not more than 180 nm, the illumination opticalsystem for guiding the exposure light from this light source to thepattern on the projection master, and the projection optical systemlocated in the optical path between the projection master and theworkpiece and guiding 25% or more by quantity of the exposure lighthaving passed through the projection master, to the workpiece to form areduced image of the pattern on the workpiece.

It is difficult to raise the sensitivity of photosensitive resin(resist) materials available for the wavelength region of not more than180 nm, as compared with those for the longer wavelengths, and, wherethe projection optical system guides only 25% or less by quantity of theexposure light from the projection master to the workpiece, it isnecessary to increase the exposure time in order to ensure a necessaryexposure dose for the resist, which will undesirably decrease thethroughput. In this case, more heat is accumulated in the projectionoptical system, so as to give rise to thermal aberration of theprojection optical system, i.e., aberration due to variations in therefractive indices of the lenses or gas and variations in indexdistribution, caused by the accumulation of heat in the projectionoptical system. This is undesirable, because projection exposure cannotbe implemented under stable imaging performance.

The projection exposure apparatus according to the embodiment of FIG. 5adopts the projection optical system PL according to the embodiment ofFIG. 1. The glass material making this projection optical system PL isfluorite as described previously and its transmittance per cm for theexposure light of 157 nm is 99 to 99.5%. Antireflection coats for theexposure light of 157 nm are those having the loss of light quantity perlens surface of 1%. From the above values, the projection exposureapparatus of FIG. 5 provided with the projection optical system of theembodiment of FIG. 1 has the transmittance of 37% and satisfies theforegoing condition.

The projection exposure method according to the present invention ispreferably a projection exposure method of projecting a reduced image ofa pattern provided in a projection master, onto a workpiece to effectexposure thereof, comprising a step of supplying exposure light in thewavelength band of not more than 200 nm; a step of guiding the exposurelight from the light source through the illumination optical system ontothe pattern on the projection master; and a step of guiding the exposurelight from the projection master through the projection optical systemonto the workpiece to form the reduced image of the pattern on theworkpiece; wherein the following condition is satisfied: $\begin{matrix}{{\frac{En4}{En3} > \frac{En2}{En1}},} & (6)\end{matrix}$

where En1 is a quantity of the exposure light incident to theillumination optical system, En2 a quantity of the exposure lighttraveling from the illumination optical system to the projection master,En3 a quantity of the exposure light incident to the projection opticalsystem, and En4 a quantity of the exposure light emerging from theprojection optical system toward the workpiece.

When the above condition (6) is not satisfied, it becomes infeasible toachieve the functions necessary for the illumination optical system,e.g., uniform illumination on the workpiece or the like, so that a finecircuit pattern cannot be transferred onto the workpiece, which isundesirable.

In the foregoing projection exposure method, the step of guiding theexposure light to the pattern preferably comprises an auxiliary step ofpassing the exposure light through a space filled with a gas atmospherehaving the low absorption property for the light in the wavelengthregion, and the step of forming the reduced image of the pattern on theworkpiece preferably comprises an auxiliary step of passing the exposurelight through a space filled with a gas atmosphere having the lowabsorption property for the light in the wavelength region.

Next described referring to the flowchart of FIG. 6 is an example ofoperation to fabricate semiconductor devices as microdevices by forminga predetermined circuit pattern on the wafer by use of the projectionexposure apparatus of the above embodiment.

First, in step 301 of FIG. 6, a metal film is evaporated onto one lot ofwafers. In next step 302, a photoresist is applied onto the metal filmon the lot of wafers. After that, in step 303, an image of a pattern ona reticle R is sequentially transferred through the projection opticalsystem PL into each shot area on the lot of wafers, using the projectionexposure apparatus of FIG. 5 provided with the projection optical systemPL of either the first or second embodiment. After that, in step 304,the photoresist on the lot of wafers is developed and thereafter in step305, etching is effected on the lot of wafers, using the resist patternas a mask, thereby forming a circuit pattern corresponding to thepattern on the reticle R, in each shot area on each wafer. After that,such devices as the semiconductor devices are fabricated by furthercarrying out formation of circuit patterns of upper layers and the like.

By the foregoing semiconductor device fabrication method, thesemiconductor devices having extremely fine circuit patterns can befabricated at high throughput.

The projection exposure apparatus of the above embodiment can also beapplied to fabrication of liquid crystal display devices asmicrodevices, by forming a predetermined circuit pattern on a plate(glass substrate). An example of operation in this application will bedescribed below referring to the flowchart of FIG. 7.

In FIG. 7, a pattern forming step 401 is a step of carrying out theso-called photolithography to transfer a pattern of a reticle onto aphotosensitive substrate (a glass substrate coated with resist, or thelike) by use of the exposure apparatus of the present embodiment. Aftercompletion of this photolithography step, a predetermined patternincluding many electrodes and others is formed on the photosensitivesubstrate. After that, the exposed substrate is processed through stepsincluding a development step, an etching step, a reticle removing step,and so on, whereby a predetermined pattern is formed on the substrate.Then the substrate is transferred to the next color filter forming step202.

Next, in the color filter forming step 402, a color filter is formed ina matrix of many sets of three dots corresponding to R (Red), G (Green),and B (Blue). Then a cell assembly step 403 is carried out after thecolor filter forming step 402.

In the cell assembly step 403, a liquid crystal panel (liquid crystalcells) is assembled using the substrate with the predetermined patternobtained in the pattern forming step 401, the color filter obtained inthe color filter forming step 402, and so on. In the cell assembly step403, for example, the liquid crystal panel (liquid crystal cells) isfabricated by charging the liquid crystal into between the substratewith the predetermined pattern obtained in the pattern forming step 401and the color filter obtained in the color filter forming step 402.

In a module assembly step 404 thereafter, a liquid crystal displaydevice is completed by mounting such components as an electric circuitfor display operation of the assembled liquid crystal panel (liquidcrystal cells), a back light, and so on.

By the foregoing liquid crystal display device fabrication method, theliquid crystal display devices having extremely fine circuit patternscan be fabricated at high throughput.

In the foregoing embodiment of FIG. 5, the fly's eye lenses 43, 46 asoptical integrators (uniformizers or homogenizers) in the illuminationoptical system can be micro-fly's eye lenses fabricated by forming aplurality of microlens surfaces on a single substrate by the techniqueof etching or the like. The first fly's eye lens 43 may be replaced by adiffractive optical element which diverges incident light by diffractionaction to form the illumination field in circular, ring, or multipolarshape in the far field (Fraunhofer diffraction region) thereof. Thediffractive optical element of this type can be one disclosed in U.S.Pat. No. 5,850,300, for example. When the diffractive optical element isemployed, the light delaying optical system 41 may be omitted.

The optical integrators can be either of internal reflection typeintegrators (rod integrators, optical pipes, optical tunnels, etc.).When an internal reflection type integrator of this kind is used, theexit surface of the internal reflection integrator becomes approximatelyconjugate with the pattern surface of the reticle. For applying it tothe aforementioned embodiment, therefore, the illumination field stop(reticle blind) 11 is located, for example, in close proximity of theexit surface of the internal reflection integrator and the zoom lens 44is constructed so as to establish the substantial conjugate relationbetween the exit surface of the first fly's eye lens 43 and the entrancesurface of the internal reflection integrator.

When the wavelength of the exposure light is not more than 180 nm, atleast either of the microlens array, diffractive optical element,internal reflection integrator, and lens elements in the illuminationoptical system is preferably made of a material selected from the groupconsisting of fluorite, silica glass doped with fluorine, silica glassdoped with fluorine and hydrogen, silica glass having the structuredetermination temperature of not more than 1200K and the hydrogenmolecule concentration of not less than 1×10¹⁷ molecules/cm³, silicaglass having the structure determination temperature of not more than1200K and the chlorine concentration of not more than 50 ppm, and silicaglass having the structure determination temperature of not more than1200K, the hydrogen molecule concentration of not less than 1×10¹⁷molecules/cm³, and the chlorine concentration of not more than 50 ppm.When the exposure wavelength is within the range of 180 nm to 200 nm(e.g., the ArF excimer laser), it is also possible to use silica glasshaving the structure determination temperature of not more than 1200Kand the OH-group concentration of not less than 1000 ppm, in addition tothe foregoing materials.

The silica glass having the structure determination temperature of notmore than 1200K and the OH-group concentration of not less than 1000 pmis disclosed in Japanese Patent No. 2770224 of Applicant of the presentapplication, and the silica glass having the structure determinationtemperature of not more than 1200K and the hydrogen moleculeconcentration of not less than 1×10¹⁷ molecules/cm³, the silica glasshaving the structure determination temperature of not more than 1200Kand the chlorine concentration of not more than 50 ppm, and the silicaglass having the structure determination temperature of not more than1200K, the hydrogen molecule concentration of not less than 1×10¹⁷molecules/cm³, and the chlorine concentration of not more than 50 ppmare disclosed in Japanese Patent No. 2936138 of Applicant of the presentapplication.

In the projection optical system PL according to the foregoing firstembodiment, each of the lens elements making the projection opticalsystem was made of fluorite, but each lens element making the projectionoptical system is preferably made of a material of at least one kindselected from the group consisting of calcium fluoride (CaF₂, fluorite),barium fluoride (BaF₂), lithium fluoride (LiF), magnesium fluoride(MgF₂), lithium calcium aluminum fluoride (LiCaAlF₆), lithium strontiumaluminum fluoride (LiSrAlF₆), and strontium fluoride (SrF₂).

In the above embodiment of FIG. 5, supposing the application of theprojection optical system PL of the first embodiment, the laser lightsource was the one for supplying the band-narrowed fluorine dimer laser(F₂ laser) of the oscillation wavelength of 157 nm, but the presentinvention is not limited to the F₂ laser. For example, the laser lightto be used can also be the band-narrowed ArF excimer laser of theoscillation wavelength of 193 nm, or the KrF excimer laser of theoscillation wavelength of 248 nm.

It is difficult to narrow the band of the laser light source in thewavelength region of wavelengths not more than 200 nm, but theapplication of the present invention relaxes the degree of bandnarrowing of the laser light source and thus presents the advantage ofdecreasing the load of achromatism of the projection optical system.

Further, the aforementioned embodiment used the F₂ laser as a lightsource, but it can be replaced by a harmonic of a solid state laser suchas the YAG laser or the like having the oscillation spectrum at 157 nm.It is also possible to use a harmonic obtained by amplifyingsingle-wavelength laser light in the infrared region or in the visibleregion, lased from a DFB semiconductor laser or a fiber laser, forexample, by a fiber amplifier doped with erbium (Er) (or doped with botherbium and ytterbium (Yb)) and converting the wavelength intoultraviolet radiation by use of a nonlinear optical crystal.

For example, when the oscillation wavelength of the single-wavelengthlaser light is in the range of 1.51 to 1.59 μm, the tenth harmonic isoutputted at the generated wavelength in the range of 151 to 159 nm. Inparticular, when the oscillation wavelength is in the range of 1.57 to1.58 μm, the tenth harmonic is obtained at the generated wavelength inthe range of 157 to 158 nm; i.e., ultraviolet radiation with thewavelength approximately equal to that of the F₂ laser light. When theoscillation wavelength is in the range of 1.03 to 1.12 μm, the seventhharmonic is outputted at the generated wavelength in the range of 147 to160 nm and, particularly, when the oscillation wavelength is in therange of 1.099 to 1.106 μm, the seventh harmonic is obtained at thegenerated wavelength in the range of 157 to 158 nm; i.e., ultravioletradiation with the wavelength approximately equal to that of the F₂laser light. An yttrium-doped fiber laser is used as thesingle-wavelength oscillation laser.

When the harmonic from the laser light source is used as describedabove, this harmonic itself has a sufficiently narrow spectral width(e.g., 0.3 pm or less) and thus it can be used instead of theaforementioned light source 2.

In the first embodiment the projection optical system was constructedusing the single kind of material, but the projection optical systemdoes not always have to be limited to the single kind material. When theprojection optical system is constructed on the premise of the exposurelight in the vacuum ultraviolet region near the far ultraviolet region,or in the far ultraviolet region as in the second embodiment, syntheticquartz and fluorite can be used as materials. When the projectionoptical system is constructed on the premise of the exposure light inthe vacuum ultraviolet region, the materials can be at least two kindsof materials selected from the group consisting of calcium fluoride(CaF₂, fluorite), barium fluoride (BaF₂), lithium fluoride (LiF),magnesium fluoride (MgF₂), lithium calcium aluminum fluoride (LiCaAlF₆),lithium strontium aluminum fluoride (LiSrAlF₆), and strontium fluoride(SrF₂). A diffractive optical element may be added to the projectionoptical system, so as to enjoy the advantage of the chromatic aberrationcorrecting effect by the diffractive optical element.

In the embodiment of FIG. 5, a prism made of a birefringent material forprevention of speckle may be placed on the entrance side of the firstfly's eye lens 43. The speckle-preventing prism of this type isdisclosed, for example, in U.S. Pat. No. 5,253,110. When the exposurelight is light with the exposure wavelength of not more than 180 nm, aprism made of a crystal of magnesium fluoride (MgF₂) can be used insteadof the quartz prism disclosed in U.S. Pat. No. 5,253,110.

This wedge prism made of the crystal of magnesium fluoride is placed soas to gradually change its thickness in the direction crossing theoptical axis of the illumination optical system. Then another wedgeprism for correction of optical path is placed opposite to the wedgeprism of the crystal of magnesium fluoride so that their apexes aredirected in opposite directions to each other. This path-correctingwedge prism has the same apex angle as the prism of the crystal ofmagnesium fluoride and is made of a light-transmitting material withoutbirefringence. This structure can align the light incident to the pairof prisms and the light emerging therefrom in the same travelingdirection.

The material of the path-correcting prism is preferably one selected,for example, from the group consisting of fluorite, silica glass dopedwith fluorine, silica glass doped with fluorine and hydrogen, silicaglass having the structure determination temperature of not more than1200K and the OH-group concentration of not less than 1000 ppm, silicaglass having the structure determination temperature of not more than1200K and the hydrogen molecule concentration of not less than 1×10¹⁷molecules/cm³, silica glass having the structure determinationtemperature of not more than 1200K and the chlorine concentration of notmore than 50 ppm, and silica glass having the structure determinationtemperature of not more than 1200K, the hydrogen molecule concentrationof not less than 1×10¹⁷ molecules/cm³, and the chlorine concentration ofnot more than 50 ppm.

The embodiment of FIG. 5 employed the step-and-scan method, but theexposure apparatus of the embodiment can be exposure apparatus of thestitching and slit scan type. When the stitching and slit scan method isemployed, the reticle and substrate are synchronously scanned in apredetermined first direction relative to the illumination area ofpredetermined shape on the reticle, thereby effecting exposure in anarea of the first column on the substrate. After that, the reticle isreplaced or the reticle is moved by a predetermined distance along asecond direction perpendicular to the first direction of the foregoingillumination area, thereby horizontally shifting the substrate in thedirection conjugate with the second direction of the illumination area.Then the reticle and substrate are again synchronously scanned in thefirst direction relative to the illumination area of the predeterminedshape on the reticle, thereby effecting exposure in an area of thesecond column on the substrate.

The exposure apparatus of this stitching and slit scan type can performexposure of the pattern of the reticle in a wider area on the substratethan the exposure field of the projection optical system. Such stitchingand slit scan type exposure apparatus are disclosed in U.S. Pat. No.5,477,304, Japanese Patent Applications Laid-Open No. H08-330220 andLaid-Open No. H10-284408, and so on.

The above embodiment can also adopt the full exposure method oftransferring the full pattern image on the reticle into a predeterminedshot area on the substrate at one time.

The embodiment of FIG. 5 was provided with only one wafer stage forholding the wafer as a workpiece (photosensitive substrate), but theapparatus may be constructed in the structure with two sets of waferstages, for example, as disclosed in Japanese Patent ApplicationsLaid-Open No. H05-175098, Laid-Open No. H10-163097, Laid-Open No.H10-163098, Laid-Open No. H10-163099, Laid-Open No. H10-214783, and soon.

Further, the present invention can not be applied only to the exposureapparatus used in fabrication of semiconductor devices, but can also beapplied to the exposure apparatus for transferring a device pattern ontoa glass plate, used in fabrication of displays including the liquidcrystal display devices and the like, the exposure apparatus fortransferring a device pattern onto a ceramic wafer, used in fabricationof thin-film magnetic heads, the exposure apparatus used in fabricationof imaging devices (CCDs etc.), and so on. The present invention canalso be applied to the exposure apparatus for transferring a circuitpattern onto a glass substrate or a silicon wafer or the like forfabrication of a reticle or a mask.

As described above, the present invention can be realized in variousconfigurations without having to be limited to the aforementionedembodiments. The disclosures in the international applicationPCT/JP99/05329 filed Sep. 29, 1999 and in the internal applicationPCT/JP99/06387 filed Nov. 16, 1999, including their respectivespecifications, scopes of claims, drawings, and abstracts all areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

As described above, the projection optical systems of the presentinvention are those capable of suppressing the chromatic aberrationthereof and reducing the loads on the light source. The correction ofchromatic aberration for the exposure light having some spectral widthcan be implemented by adding a single kind of glass material or thesmall number of color-correcting glass materials.

By the projection exposure apparatus and methods according to thepresent invention, it is feasible to obtain the very fine circuitpatterns of microdevices while simplifying the structure of theprojection optical system.

By the device fabrication methods according to the present invention,the very fine circuit patterns of microdevices can be obtained without adrop in throughput.

What is claimed is:
 1. A dioptric projection optical system for formingan image of a pattern on a first surface, onto a second surface byaction of radiation-transmitting refractors, comprising: a front lensunit having a positive refracting power, located in an optical pathbetween said first surface and said second surface; a rear lens unithaving a positive refracting power, located in an optical path betweensaid front lens unit and said second surface; and an aperture stoplocated in the vicinity of a rear focal point position of said frontlens unit; said projection optical system being telecentric on the saidfirst surface side and on the said second surface side, wherein thefollowing condition is satisfied: 0.065<f2/L<0.125, where f2 is a focallength of said rear lens unit and L is a distance from said firstsurface to said second surface.
 2. The projection optical systemaccording to claim 1, said projection optical system comprising at leastone lens surface of aspheric shape.
 3. The projection optical systemaccording to claim 2, wherein when six lenses are selected in order fromthe said first surface side of lenses having their respective refractingpowers in said projection optical system, at least one surface of thesix lenses has an aspheric shape having a negative refracting power. 4.The projection optical system according to claim 1, wherein said frontlens unit comprises a first lens unit with a negative refracting power,a second lens unit with a positive refracting power, a third lens unitwith a negative refracting power, and a fourth lens unit with a positiverefracting power in the order named from the first surface side, whereinthe following conditions are satisfied: −1.3<1/β1<0, and 0.08<L1/L<0.17,where β1 is a composite, lateral magnification of said first lens unitand said second lens unit, L1 is a distance from said first surface to alens surface closest to said second surface in said second lens unit,and L is the distance from said first surface to said second surface. 5.The projection optical system according to claim 4, wherein said firstand second lens units include at least two lens surfaces of asphericshape and comprise ten or more lenses.
 6. The projection optical systemaccording to claim 1, wherein said front lens unit comprises a firstlens unit with a negative refracting power, a second lens unit with apositive refracting power, a third lens unit with a negative refractingpower, and a fourth lens unit with a positive refracting power in theorder named from the first surface side.
 7. The projection opticalsystem according to claim 4, wherein the following condition issatisfied: 0.46<C/L<0.64, where C is a total thickness along the opticalaxis of the radiation-transmitting refractors located in the opticalpath of said projection optical system and L is the distance from saidfirst surface to said second surface.
 8. The projection optical systemaccording to claim 1, wherein the following condition is satisfied:0.15<Ea/E<0.7, where E is the total number of members having theirrespective refracting powers among radiation-transmitting refractors insaid projection optical system and Ea is the total number of memberseach provided with a lens surface of aspheric shape.
 9. The projectionoptical system according to claim 8, wherein the total number of saidmembers having their respective refracting powers is not less than 16.10. The projection optical system according to claim 8, wherein thetotal number of said members having their respective refracting powersis not more than
 26. 11. The projection optical system according toclaim 8, wherein radiation-transmitting refractors in said projectionoptical system are made of a single kind of material.
 12. The projectionoptical system according to claim 8, wherein the radiation-transmittingrefractors in said projection optical system comprise firstradiation-transmitting refractors made of a first material and secondradiation-transmitting refractors made of a second material, and whereina percentage of the number of said second radiation-transmittingrefractors to the number of the members having their respectiverefracting powers among said radiation-transmitting refractors, is notmore than 32%.
 13. The projection optical system according to claim 1,said projection optical system forming a reduced image of said patternon said first surface, on said second surface.
 14. The projectionoptical system according to claim 1, wherein said aperture stop islocated in an optical path between said front lens unit and said rearlens unit.
 15. A method of fabricating a dioptric projection opticalsystem for forming an image of a pattern on a first surface, onto asecond surface by action of radiation-transmitting refractors,comprising: a step of locating a front lens unit having a positiverefracting power; a step of locating a rear lens unit having a positiverefracting power, between the front lens unit and said second surface;and a step of locating an aperture stop between said front lens unit andsaid rear lens unit; wherein said front lens unit, said rear lens unit,and said aperture stop are located so that the projection optical systemis telecentric on the said first surface side and on the said secondsurface side, and said method using the projection optical systemsatisfying the following condition: 0.0065<f2/L<0.125,  where f2 is afocal length of said rear lens unit and L is a distance from said firstsurface to said second surface.
 16. A projection exposure apparatus forprojecting a reduced image of a pattern provided on a projection master,onto a workpiece to effect exposure thereof, comprising: a light sourcefor supplying exposure light; an illumination optical system for guidingthe exposure light from the light source to said pattern on saidprojection master; and the projection optical system as set forth inclaim 1; wherein said projection master can be placed on said firstsurface of said projection optical system, and said workpiece can beplaced on said second surface.
 17. A projection exposure apparatus forprojecting a reduced image of a pattern provided on a projection master,onto a workpiece to effect exposure thereof while scanning, comprising:a light source for supplying exposure light; an illumination opticalsystem for guiding the exposure light from the light source to saidpattern on said projection master; the projection optical system as setforth in claim 1; a first stage for enabling said projection master tobe placed on said first surface of said projection optical system; and asecond stage for enabling said workpiece to be placed on said secondsurface; wherein said first and second stages are movable at a ratio ofspeeds according to a projection magnification of said projectionoptical system.
 18. The projection exposure apparatus according to claim16, wherein said light source supplies the exposure light in awavelength region of not more than 180 nm and wherein said projectionoptical system guides 25% or more by quantity of the exposure light fromsaid projection master, to said workpiece.
 19. A projection exposuremethod of projecting a pattern formed on a projection master, onto aworkpiece to effect exposure thereof, which uses the projection exposureapparatus as set forth in claim 16, wherein said projection master isplaced on said first surface and said workpiece is placed on said secondsurface, and wherein an image of said pattern is formed on saidworkpiece through said projection optical system.
 20. A method offabricating a microdevice having a predetermined circuit pattern,comprising: a step of projecting an image of said pattern onto saidworkpiece to effect exposure thereof, using the projection exposuremethod as set forth in claim 19, and a step of developing said workpieceafter the projection exposure.